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• How to use Object Type Converter

  - by arun.x.sridharan(at)oracle.com

  UseCase Description A person form where in user will enter String which has to be converted to Number while persisting. From the User Interface we might be getting a String value which has to be persisted in the database as a number in that scenario we can use converters to map the java object which is of type String to its database value which is a Number. For example , there is a 'Person' table in database which is used to store the user details passed from the User Interface. It has a 'Status' column which is of the value  Number. But from the User Interface String values (Active/InActive) are passed . For persisting the user details we can use Object type converter and provide the mappings for status column corresponding to the String values. Object type converter can be used if you wanted to have a mapping for a field for example when departmentName on the entity was of String value and mapped to dept_name field on the database table which is of the value NUMBER.   Implementation steps Sample EJB API for setting the value of status on Person Entity as a String     public void createPerson(String status,String firstName,String lastName) {                Person person = new Person();                // status will be set as a String value received from the User Interface         person.setStatus(status);                person.setFirstname(firstName);        person.setLastname(lastName);                persistPerson(person);         } In the sample code shown above status is passed as a String, this has to be converted to Number. The String value obtained will be set on Person object and persistPerson API will be called for creating a new person from the values passed from the User Interface.  Steps to configure Object type converter: 1. Navigate to Person Entity from persistence.xml and navigate to status field2. Click on Conversion tab and select Converted check box3. Select Object Type Converter radio button and set the Data Type Class to      java.math.BigDecimal and Object Type Class to java.lang.String4. Specify the conversion values for all the values that can be passed from the user interface  as shown below5. Set the Default Object value

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• How can I get type information at runtime from a DMP file in a Windbg extension?

  - by pj4533

  This is related to my previous question, regarding pulling objects from a dmp file. As I mentioned in the previous question, I can successfully pull object out of the dmp file by creating wrapper 'remote' objects. I have implemented several of these so far, and it seems to be working well. However I have run into a snag. In one case, a pointer is stored in a class, say of type 'SomeBaseClass', but that object is actually of the type 'SomeDerivedClass' which derives from 'SomeBaseClass'. For example it would be something like this: MyApplication!SomeObject +0x000 field1 : Ptr32 SomeBaseClass +0x004 field2 : Ptr32 SomeOtherClass +0x008 field3 : Ptr32 SomeOtherClass I need someway to find out what the ACTUAL type of 'field1' is. To be more specific, using example addresses: MyApplication!SomeObject +0x000 field1 : 0cae2e24 SomeBaseClass +0x004 field2 : 0x262c8d3c SomeOtherClass +0x008 field3 : 0x262c8d3c SomeOtherClass 0:000> dt SomeBaseClass 0cae2e24 MyApplication!SomeBaseClass +0x000 __VFN_table : 0x02de89e4 +0x038 basefield1 : (null) +0x03c basefield2 : 3 0:000> dt SomeDerivedClass 0cae2e24 MyApplication!SomeDerivedClass +0x000 __VFN_table : 0x02de89e4 +0x038 basefield1 : (null) +0x03c basefield2 : 3 +0x040 derivedfield1 : 357 +0x044 derivedfield2 : timecode_t When I am in WinDbg, I can do this: dt 0x02de89e4 And it will show the type: 0:000> dt 0x02de89e4 SomeDerivedClass::`vftable' Symbol not found. But how do get that inside an extension? Can I use SearchMemory() to look for 'SomeDerivedClass::`vftable'? If you follow my other question, I need this type information so I know what type of wrapper remote classes to create. I figure it might end up being some sort of case-statement, where I have to match a string to a type? I am ok with that, but I still don't know where I can get that string that represents the type of the object in question (ie SomeObject-field1 in the above example).

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• PyML 0.7.2 - How to prevent accuracy from dropping after storing/loading a classifier?

  - by Michael Aaron Safyan

  This is a followup from "Save PyML.classifiers.multi.OneAgainstRest(SVM()) object?". The solution to that question was close, but not quite right, (the SparseDataSet is broken, so attempting to save/load with that dataset container type will fail, no matter what. Also, PyML is inconsistent in terms of whether labels should be numbers or strings... it turns out that the oneAgainstRest function is actually not good enough, because the labels need to be strings and simultaneously convertible to floats, because there are places where it is assumed to be a string and elsewhere converted to float) and so after a great deal of hacking and such I was finally able to figure out a way to save and load my multi-class classifier without it blowing up with an error.... however, although it is no longer giving me an error message, it is still not quite right as the accuracy of the classifier drops significantly when it is saved and then reloaded (so I'm still missing a piece of the puzzle). I am currently using the following custom mutli-class classifier for training, saving, and loading: class SVM(object): def __init__(self,features_or_filename,labels=None,kernel=None): if isinstance(features_or_filename,str): filename=features_or_filename; if labels!=None: raise ValueError,"Labels must be None if loading from a file."; with open(os.path.join(filename,"uniquelabels.list"),"rb") as uniquelabelsfile: self.uniquelabels=sorted(list(set(pickle.load(uniquelabelsfile)))); self.labeltoindex={}; for idx,label in enumerate(self.uniquelabels): self.labeltoindex[label]=idx; self.classifiers=[]; for classidx, classname in enumerate(self.uniquelabels): self.classifiers.append(PyML.classifiers.svm.loadSVM(os.path.join(filename,str(classname)+".pyml.svm"),datasetClass = PyML.VectorDataSet)); else: features=features_or_filename; if labels==None: raise ValueError,"Labels must not be None when training."; self.uniquelabels=sorted(list(set(labels))); self.labeltoindex={}; for idx,label in enumerate(self.uniquelabels): self.labeltoindex[label]=idx; points = [[float(xij) for xij in xi] for xi in features]; self.classifiers=[PyML.SVM(kernel) for label in self.uniquelabels]; for i in xrange(len(self.uniquelabels)): currentlabel=self.uniquelabels[i]; currentlabels=['+1' if k==currentlabel else '-1' for k in labels]; currentdataset=PyML.VectorDataSet(points,L=currentlabels,positiveClass='+1'); self.classifiers[i].train(currentdataset,saveSpace=False); def accuracy(self,pts,labels): logger=logging.getLogger("ml"); correct=0; total=0; classindexes=[self.labeltoindex[label] for label in labels]; h=self.hypotheses(pts); for idx in xrange(len(pts)): if h[idx]==classindexes[idx]: logger.info("RIGHT: Actual \"%s\" == Predicted \"%s\"" %(self.uniquelabels[ classindexes[idx] ], self.uniquelabels[ h[idx] ])); correct+=1; else: logger.info("WRONG: Actual \"%s\" != Predicted \"%s\"" %(self.uniquelabels[ classindexes[idx] ], self.uniquelabels[ h[idx] ])) total+=1; return float(correct)/float(total); def prediction(self,pt): h=self.hypothesis(pt); if h!=None: return self.uniquelabels[h]; return h; def predictions(self,pts): h=self.hypotheses(self,pts); return [self.uniquelabels[x] if x!=None else None for x in h]; def hypothesis(self,pt): bestvalue=None; bestclass=None; dataset=PyML.VectorDataSet([pt]); for classidx, classifier in enumerate(self.classifiers): val=classifier.decisionFunc(dataset,0); if (bestvalue==None) or (val>bestvalue): bestvalue=val; bestclass=classidx; return bestclass; def hypotheses(self,pts): bestvalues=[None for pt in pts]; bestclasses=[None for pt in pts]; dataset=PyML.VectorDataSet(pts); for classidx, classifier in enumerate(self.classifiers): for ptidx in xrange(len(pts)): val=classifier.decisionFunc(dataset,ptidx); if (bestvalues[ptidx]==None) or (val>bestvalues[ptidx]): bestvalues[ptidx]=val; bestclasses[ptidx]=classidx; return bestclasses; def save(self,filename): if not os.path.exists(filename): os.makedirs(filename); with open(os.path.join(filename,"uniquelabels.list"),"wb") as uniquelabelsfile: pickle.dump(self.uniquelabels,uniquelabelsfile,pickle.HIGHEST_PROTOCOL); for classidx, classname in enumerate(self.uniquelabels): self.classifiers[classidx].save(os.path.join(filename,str(classname)+".pyml.svm")); I am using the latest version of PyML (0.7.2, although PyML.__version__ is 0.7.0). When I construct the classifier with a training dataset, the reported accuracy is ~0.87. When I then save it and reload it, the accuracy is less than 0.001. So, there is something here that I am clearly not persisting correctly, although what that may be is completely non-obvious to me. Would you happen to know what that is?

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• PyML 0.7.2 - How to prevent accuracy from dropping after stroing/loading a classifier?

  - by Michael Aaron Safyan

  This is a followup from "Save PyML.classifiers.multi.OneAgainstRest(SVM()) object?". The solution to that question was close, but not quite right, (the SparseDataSet is broken, so attempting to save/load with that dataset container type will fail, no matter what. Also, PyML is inconsistent in terms of whether labels should be numbers or strings... it turns out that the oneAgainstRest function is actually not good enough, because the labels need to be strings and simultaneously convertible to floats, because there are places where it is assumed to be a string and elsewhere converted to float) and so after a great deal of hacking and such I was finally able to figure out a way to save and load my multi-class classifier without it blowing up with an error.... however, although it is no longer giving me an error message, it is still not quite right as the accuracy of the classifier drops significantly when it is saved and then reloaded (so I'm still missing a piece of the puzzle). I am currently using the following custom mutli-class classifier for training, saving, and loading: class SVM(object): def __init__(self,features_or_filename,labels=None,kernel=None): if isinstance(features_or_filename,str): filename=features_or_filename; if labels!=None: raise ValueError,"Labels must be None if loading from a file."; with open(os.path.join(filename,"uniquelabels.list"),"rb") as uniquelabelsfile: self.uniquelabels=sorted(list(set(pickle.load(uniquelabelsfile)))); self.labeltoindex={}; for idx,label in enumerate(self.uniquelabels): self.labeltoindex[label]=idx; self.classifiers=[]; for classidx, classname in enumerate(self.uniquelabels): self.classifiers.append(PyML.classifiers.svm.loadSVM(os.path.join(filename,str(classname)+".pyml.svm"),datasetClass = PyML.VectorDataSet)); else: features=features_or_filename; if labels==None: raise ValueError,"Labels must not be None when training."; self.uniquelabels=sorted(list(set(labels))); self.labeltoindex={}; for idx,label in enumerate(self.uniquelabels): self.labeltoindex[label]=idx; points = [[float(xij) for xij in xi] for xi in features]; self.classifiers=[PyML.SVM(kernel) for label in self.uniquelabels]; for i in xrange(len(self.uniquelabels)): currentlabel=self.uniquelabels[i]; currentlabels=['+1' if k==currentlabel else '-1' for k in labels]; currentdataset=PyML.VectorDataSet(points,L=currentlabels,positiveClass='+1'); self.classifiers[i].train(currentdataset,saveSpace=False); def accuracy(self,pts,labels): logger=logging.getLogger("ml"); correct=0; total=0; classindexes=[self.labeltoindex[label] for label in labels]; h=self.hypotheses(pts); for idx in xrange(len(pts)): if h[idx]==classindexes[idx]: logger.info("RIGHT: Actual \"%s\" == Predicted \"%s\"" %(self.uniquelabels[ classindexes[idx] ], self.uniquelabels[ h[idx] ])); correct+=1; else: logger.info("WRONG: Actual \"%s\" != Predicted \"%s\"" %(self.uniquelabels[ classindexes[idx] ], self.uniquelabels[ h[idx] ])) total+=1; return float(correct)/float(total); def prediction(self,pt): h=self.hypothesis(pt); if h!=None: return self.uniquelabels[h]; return h; def predictions(self,pts): h=self.hypotheses(self,pts); return [self.uniquelabels[x] if x!=None else None for x in h]; def hypothesis(self,pt): bestvalue=None; bestclass=None; dataset=PyML.VectorDataSet([pt]); for classidx, classifier in enumerate(self.classifiers): val=classifier.decisionFunc(dataset,0); if (bestvalue==None) or (val>bestvalue): bestvalue=val; bestclass=classidx; return bestclass; def hypotheses(self,pts): bestvalues=[None for pt in pts]; bestclasses=[None for pt in pts]; dataset=PyML.VectorDataSet(pts); for classidx, classifier in enumerate(self.classifiers): for ptidx in xrange(len(pts)): val=classifier.decisionFunc(dataset,ptidx); if (bestvalues[ptidx]==None) or (val>bestvalues[ptidx]): bestvalues[ptidx]=val; bestclasses[ptidx]=classidx; return bestclasses; def save(self,filename): if not os.path.exists(filename): os.makedirs(filename); with open(os.path.join(filename,"uniquelabels.list"),"wb") as uniquelabelsfile: pickle.dump(self.uniquelabels,uniquelabelsfile,pickle.HIGHEST_PROTOCOL); for classidx, classname in enumerate(self.uniquelabels): self.classifiers[classidx].save(os.path.join(filename,str(classname)+".pyml.svm")); I am using the latest version of PyML (0.7.2, although PyML.__version__ is 0.7.0). When I construct the classifier with a training dataset, the reported accuracy is ~0.87. When I then save it and reload it, the accuracy is less than 0.001. So, there is something here that I am clearly not persisting correctly, although what that may be is completely non-obvious to me. Would you happen to know what that is?

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• AutoMapper MappingFunction from Source Type of NameValueCollection

  - by REA_ANDREW

  I have had a situation arise today where I need to construct a complex type from a source of a NameValueCollection.  A little while back I submitted a patch for the Agatha Project to include REST (JSON and XML) support for the service contract.  I realized today that as useful as it is, it did not actually support true REST conformance, as REST should support GET so that you can use JSONP from JavaScript directly meaning you can query cross domain services.  My original implementation for POX and JSON used the POST method and this immediately rules out JSONP as from reading, JSONP only works with GET Requests. This then raised another issue.  The current operation contract of Agatha and one of its main benefits is that you can supply an array of Request objects in a single request, limiting the about of server requests you need to make.  Now, at the present time I am thinking that this will not be the case for the REST imlementation but will yield the benefits of the fact that : The same Request objects can be used for SOAP and RST (POX, JSON) The construct of the JavaScript functions will be simpler and more readable It will enable the use of JSONP for cross domain REST Services The current contract for the Agatha WcfRequestProcessor is at time of writing the following: [ServiceContract] public interface IWcfRequestProcessor { [OperationContract(Name = "ProcessRequests")] [ServiceKnownType("GetKnownTypes", typeof(KnownTypeProvider))] [TransactionFlow(TransactionFlowOption.Allowed)] Response[] Process(params Request[] requests); [OperationContract(Name = "ProcessOneWayRequests", IsOneWay = true)] [ServiceKnownType("GetKnownTypes", typeof(KnownTypeProvider))] void ProcessOneWayRequests(params OneWayRequest[] requests); }   My current proposed solution, and at the very early stages of my concept is as follows: [ServiceContract] public interface IWcfRestJsonRequestProcessor { [OperationContract(Name="process")] [ServiceKnownType("GetKnownTypes", typeof(KnownTypeProvider))] [TransactionFlow(TransactionFlowOption.Allowed)] [WebGet(UriTemplate = "process/{name}/{*parameters}", BodyStyle = WebMessageBodyStyle.WrappedResponse, ResponseFormat = WebMessageFormat.Json)] Response[] Process(string name, NameValueCollection parameters); [OperationContract(Name="processoneway",IsOneWay = true)] [ServiceKnownType("GetKnownTypes", typeof(KnownTypeProvider))] [WebGet(UriTemplate = "process-one-way/{name}/{*parameters}", BodyStyle = WebMessageBodyStyle.WrappedResponse, ResponseFormat = WebMessageFormat.Json)] void ProcessOneWayRequests(string name, NameValueCollection parameters); }   Now this part I have not yet implemented, it is the preliminart step which I have developed which will allow me to take the name of the Request Type and the NameValueCollection and construct the complex type which is that of the Request which I can then supply to a nested instance of the original IWcfRequestProcessor  and work as it should normally.  To give an example of some of the urls which you I envisage with this method are: http://www.url.com/service.svc/json/process/getweather/?location=london http://www.url.com/service.svc/json/process/getproductsbycategory/?categoryid=1 http://www.url.om/service.svc/json/process/sayhello/?name=andy Another reason why my direction has gone to a single request for the REST implementation is because of restrictions which are imposed by browsers on the length of the url.  From what I have read this is on average 2000 characters.  I think that this is a very acceptable usage limit in the context of using 1 request, but I do not think this is acceptable for accommodating multiple requests chained together.  I would love to be corrected on that one, I really would but unfortunately from what I have read I have come to the conclusion that this is not the case. The mapping function So, as I say this is just the first pass I have made at this, and I am not overly happy with the try catch for detecting types without default constructors.  I know there is a better way but for the minute, it escapes me.  I would also like to know the correct way for adding mapping functions and not using the anonymous way that I have used.  To achieve this I have used recursion which I am sure is what other mapping function use. As you do have to go as deep as the complex type is. public static object RecurseType(NameValueCollection collection, Type type, string prefix) { try { var returnObject = Activator.CreateInstance(type); foreach (var property in type.GetProperties()) { foreach (var key in collection.AllKeys) { if (String.IsNullOrEmpty(prefix) || key.Length > prefix.Length) { var propertyNameToMatch = String.IsNullOrEmpty(prefix) ? key : key.Substring(property.Name.IndexOf(prefix) + prefix.Length + 1); if (property.Name == propertyNameToMatch) { property.SetValue(returnObject, Convert.ChangeType(collection.Get(key), property.PropertyType), null); } else if(property.GetValue(returnObject,null) == null) { property.SetValue(returnObject, RecurseType(collection, property.PropertyType, String.Concat(prefix, property.PropertyType.Name)), null); } } } } return returnObject; } catch (MissingMethodException) { //Quite a blunt way of dealing with Types without default constructor return null; } }   Another thing is performance, I have not measured this in anyway, it is as I say the first pass, so I hope this can be the start of a more perfected implementation.  I tested this out with a complex type of three levels, there is no intended logical meaning to the properties, they are simply for the purposes of example.  You could call this a spiking session, as from here on in, now I know what I am building I would take a more TDD approach.  OK, purists, why did I not do this from the start, well I didn’t, this was a brain dump and now I know what I am building I can. The console test and how I used with AutoMapper is as follows: static void Main(string[] args) { var collection = new NameValueCollection(); collection.Add("Name", "Andrew Rea"); collection.Add("Number", "1"); collection.Add("AddressLine1", "123 Street"); collection.Add("AddressNumber", "2"); collection.Add("AddressPostCodeCountry", "United Kingdom"); collection.Add("AddressPostCodeNumber", "3"); AutoMapper.Mapper.CreateMap<NameValueCollection, Person>() .ConvertUsing(x => { return(Person) RecurseType(x, typeof(Person), null); }); var person = AutoMapper.Mapper.Map<NameValueCollection, Person>(collection); Console.WriteLine(person.Name); Console.WriteLine(person.Number); Console.WriteLine(person.Address.Line1); Console.WriteLine(person.Address.Number); Console.WriteLine(person.Address.PostCode.Country); Console.WriteLine(person.Address.PostCode.Number); Console.ReadLine(); }   Notice the convention that I am using and that this method requires you do use.  Each property is prefixed with the constructed name of its parents combined.  This is the convention used by AutoMapper and it makes sense. I can also think of other uses for this including using with ASP.NET MVC ModelBinders for creating a complex type from the QueryString which is itself is a NameValueCollection. Hope this is of some help to people and I would welcome any code reviews you could give me. References: Agatha : http://code.google.com/p/agatha-rrsl/ AutoMapper : http://automapper.codeplex.com/   Cheers for now, Andrew   P.S. I will have the proposed solution for a more complete REST implementation for AGATHA very soon. 

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• Dynamic Type to do away with Reflection

  - by Rick Strahl

  The dynamic type in C# 4.0 is a welcome addition to the language. One thing I’ve been doing a lot with it is to remove explicit Reflection code that’s often necessary when you ‘dynamically’ need to walk and object hierarchy. In the past I’ve had a number of ReflectionUtils that used string based expressions to walk an object hierarchy. With the introduction of dynamic much of the ReflectionUtils code can be removed for cleaner code that runs considerably faster to boot. The old Way - Reflection Here’s a really contrived example, but assume for a second, you’d want to dynamically retrieve a Page.Request.Url.AbsoluteUrl based on a Page instance in an ASP.NET Web Page request. The strongly typed version looks like this: string path = Page.Request.Url.AbsolutePath; Now assume for a second that Page wasn’t available as a strongly typed instance and all you had was an object reference to start with and you couldn’t cast it (right I said this was contrived :-)) If you’re using raw Reflection code to retrieve this you’d end up writing 3 sets of Reflection calls using GetValue(). Here’s some internal code I use to retrieve Property values as part of ReflectionUtils: /// <summary> /// Retrieve a property value from an object dynamically. This is a simple version /// that uses Reflection calls directly. It doesn't support indexers. /// </summary> /// <param name="instance">Object to make the call on</param> /// <param name="property">Property to retrieve</param> /// <returns>Object - cast to proper type</returns> public static object GetProperty(object instance, string property) { return instance.GetType().GetProperty(property, ReflectionUtils.MemberAccess).GetValue(instance, null); } If you want more control over properties and support both fields and properties as well as array indexers a little more work is required: /// <summary> /// Parses Properties and Fields including Array and Collection references. /// Used internally for the 'Ex' Reflection methods. /// </summary> /// <param name="Parent"></param> /// <param name="Property"></param> /// <returns></returns> private static object GetPropertyInternal(object Parent, string Property) { if (Property == "this" || Property == "me") return Parent; object result = null; string pureProperty = Property; string indexes = null; bool isArrayOrCollection = false; // Deal with Array Property if (Property.IndexOf("[") > -1) { pureProperty = Property.Substring(0, Property.IndexOf("[")); indexes = Property.Substring(Property.IndexOf("[")); isArrayOrCollection = true; } // Get the member MemberInfo member = Parent.GetType().GetMember(pureProperty, ReflectionUtils.MemberAccess)[0]; if (member.MemberType == MemberTypes.Property) result = ((PropertyInfo)member).GetValue(Parent, null); else result = ((FieldInfo)member).GetValue(Parent); if (isArrayOrCollection) { indexes = indexes.Replace("[", string.Empty).Replace("]", string.Empty); if (result is Array) { int Index = -1; int.TryParse(indexes, out Index); result = CallMethod(result, "GetValue", Index); } else if (result is ICollection) { if (indexes.StartsWith("\"")) { // String Index indexes = indexes.Trim('\"'); result = CallMethod(result, "get_Item", indexes); } else { // assume numeric index int index = -1; int.TryParse(indexes, out index); result = CallMethod(result, "get_Item", index); } } } return result; } /// <summary> /// Returns a property or field value using a base object and sub members including . syntax. /// For example, you can access: oCustomer.oData.Company with (this,"oCustomer.oData.Company") /// This method also supports indexers in the Property value such as: /// Customer.DataSet.Tables["Customers"].Rows[0] /// </summary> /// <param name="Parent">Parent object to 'start' parsing from. Typically this will be the Page.</param> /// <param name="Property">The property to retrieve. Example: 'Customer.Entity.Company'</param> /// <returns></returns> public static object GetPropertyEx(object Parent, string Property) { Type type = Parent.GetType(); int at = Property.IndexOf("."); if (at < 0) { // Complex parse of the property return GetPropertyInternal(Parent, Property); } // Walk the . syntax - split into current object (Main) and further parsed objects (Subs) string main = Property.Substring(0, at); string subs = Property.Substring(at + 1); // Retrieve the next . section of the property object sub = GetPropertyInternal(Parent, main); // Now go parse the left over sections return GetPropertyEx(sub, subs); } As you can see there’s a fair bit of code involved into retrieving a property or field value reliably especially if you want to support array indexer syntax. This method is then used by a variety of routines to retrieve individual properties including one called GetPropertyEx() which can walk the dot syntax hierarchy easily. Anyway with ReflectionUtils I can  retrieve Page.Request.Url.AbsolutePath using code like this: string url = ReflectionUtils.GetPropertyEx(Page, "Request.Url.AbsolutePath") as string; This works fine, but is bulky to write and of course requires that I use my custom routines. It’s also quite slow as the code in GetPropertyEx does all sorts of string parsing to figure out which members to walk in the hierarchy. Enter dynamic – way easier! .NET 4.0’s dynamic type makes the above really easy. The following code is all that it takes: object objPage = Page; // force to object for contrivance :) dynamic page = objPage; // convert to dynamic from untyped object string scriptUrl = page.Request.Url.AbsolutePath; The dynamic type assignment in the first two lines turns the strongly typed Page object into a dynamic. The first assignment is just part of the contrived example to force the strongly typed Page reference into an untyped value to demonstrate the dynamic member access. The next line then just creates the dynamic type from the Page reference which allows you to access any public properties and methods easily. It also lets you access any child properties as dynamic types so when you look at Intellisense you’ll see something like this when typing Request.: In other words any dynamic value access on an object returns another dynamic object which is what allows the walking of the hierarchy chain. Note also that the result value doesn’t have to be explicitly cast as string in the code above – the compiler is perfectly happy without the cast in this case inferring the target type based on the type being assigned to. The dynamic conversion automatically handles the cast when making the final assignment which is nice making for natural syntnax that looks *exactly* like the fully typed syntax, but is completely dynamic. Note that you can also use indexers in the same natural syntax so the following also works on the dynamic page instance: string scriptUrl = page.Request.ServerVariables["SCRIPT_NAME"]; The dynamic type is going to make a lot of Reflection code go away as it’s simply so much nicer to be able to use natural syntax to write out code that previously required nasty Reflection syntax. Another interesting thing about the dynamic type is that it actually works considerably faster than Reflection. Check out the following methods that check performance: void Reflection() { Stopwatch stop = new Stopwatch(); stop.Start(); for (int i = 0; i < reps; i++) { // string url = ReflectionUtils.GetProperty(Page,"Title") as string;// "Request.Url.AbsolutePath") as string; string url = Page.GetType().GetProperty("Title", ReflectionUtils.MemberAccess).GetValue(Page, null) as string; } stop.Stop(); Response.Write("Reflection: " + stop.ElapsedMilliseconds.ToString()); } void Dynamic() { Stopwatch stop = new Stopwatch(); stop.Start(); dynamic page = Page; for (int i = 0; i < reps; i++) { string url = page.Title; //Request.Url.AbsolutePath; } stop.Stop(); Response.Write("Dynamic: " + stop.ElapsedMilliseconds.ToString()); } The dynamic code runs in 4-5 milliseconds while the Reflection code runs around 200+ milliseconds! There’s a bit of overhead in the first dynamic object call but subsequent calls are blazing fast and performance is actually much better than manual Reflection. Dynamic is definitely a huge win-win situation when you need dynamic access to objects at runtime.© Rick Strahl, West Wind Technologies, 2005-2010Posted in .NET  CSharp  

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• How do I add a trailing slash for Django MPTT-based categorization app?

  - by Patrick Beeson

  I'm using Django-MPTT to develop a categorization app for my Django project. But I can't seem to get the regex pattern for adding a trailing slash that doesn't also break on child categories. Here's an example URL: http://mydjangoapp.com/categories/parentcat/childcat/ I'd like to be able to use http://mydjangoapp.com/categories/parentcat and have it redirect to the trailing slash version. The same should apply to http://mydjangoapp.com/categories/parentcat/childcat (it should redirect to http://mydjangoapp.com/categories/parentcat/childcat/). Here's my urls.py: from django.conf.urls.defaults import patterns, include, url from django.views.decorators.cache import cache_page from storefront.categories.models import Category from storefront.categories.views import SimpleCategoryView urlpatterns = patterns('', url(r'^(?P<full_slug>[-\w/]+)', cache_page(SimpleCategoryView.as_view(), 60 * 15), name='category_view'), ) And here is my view: from django.core.exceptions import ImproperlyConfigured from django.core.urlresolvers import reverse from django.views.generic import TemplateView, DetailView from django.views.generic.detail import SingleObjectTemplateResponseMixin, SingleObjectMixin from django.utils.translation import ugettext as _ from django.contrib.syndication.views import Feed from storefront.categories.models import Category class SimpleCategoryView(TemplateView): def get_category(self): return Category.objects.get(full_slug=self.kwargs['full_slug']) def get_context_data(self, **kwargs): context = super(SimpleCategoryView, self).get_context_data(**kwargs) context["category"] = self.get_category() return context def get_template_names(self): if self.get_category().template_name: return [self.get_category().template_name] else: return ['categories/category_detail.html'] And finally, my model: from django.db import models from mptt.models import MPTTModel from mptt.fields import TreeForeignKey class CategoryManager(models.Manager): def get(self, **kwargs): defaults = {} defaults.update(kwargs) if 'full_slug' in defaults: if defaults['full_slug'] and defaults['full_slug'][-1] != "/": defaults['full_slug'] += "/" return super(CategoryManager, self).get(**defaults) class Category(MPTTModel): title = models.CharField(max_length=255) description = models.TextField(blank=True, help_text='Please use <a href="http://daringfireball.net/projects/markdown/syntax">Markdown syntax</a> for all text-formatting and links. No HTML is allowed.') slug = models.SlugField(help_text='Prepopulates from title field.') full_slug = models.CharField(max_length=255, blank=True) template_name = models.CharField(max_length=70, blank=True, help_text="Example: 'categories/category_parent.html'. If this isn't provided, the system will use 'categories/category_detail.html'. Use 'categories/category_parent.html' for all parent categories and 'categories/category_child.html' for all child categories.") parent = TreeForeignKey('self', null=True, blank=True, related_name='children') objects = CategoryManager() class Meta: verbose_name = 'category' verbose_name_plural = 'categories' def save(self, *args, **kwargs): orig_full_slug = self.full_slug if self.parent: self.full_slug = "%s%s/" % (self.parent.full_slug, self.slug) else: self.full_slug = "%s/" % self.slug obj = super(Category, self).save(*args, **kwargs) if orig_full_slug != self.full_slug: for child in self.get_children(): child.save() return obj def available_product_set(self): """ Returns available, prioritized products for a category """ from storefront.apparel.models import Product return self.product_set.filter(is_available=True).order_by('-priority') def __unicode__(self): return "%s (%s)" % (self.title, self.full_slug) def get_absolute_url(self): return '/categories/%s' % (self.full_slug)

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• Doctrine generate models - problem with relation type

  - by mrok

  I am trying generate doctrine models from yaml schema I have schema like that: Product: columns: id: type: integer(5) primary: true unsigned: true autoincrement: true activation_time: type: datetime notnull: true enduser_id: type: integer(5) unsigned: true notnull: true relations: Enduser: foreignType: one type: one foreignAlias: Product Hostid: columns: id: type: integer(5) primary: true unsigned: true autoincrement: true value: type: string(32) fixed: true notnull: true Order: columns: id: type: integer(5) primary: true autoincrement: true unsigned: true expire_date: type: datetime description: type: clob Enduser: columns: id: type: integer(5) primary: true unsigned: true autoincrement: true hostid_id: type: integer(5) unsigned: true notnull: true order_id: type: integer(5) unsigned: true notnull: true relations: Order: foreignAlias: Endusers Hostid: foreignAlias: Endusers and the problem is that models generated by doctrine generate-models-yaml are wrong in BaseEnduser $Product is defined as Doctrine_Collection $this-hasMany('Product', array( 'local' = 'id', 'foreign' = 'enduser_id')); instead just Product object what did I wrong? relation is defined as foreignType: one type: one

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• Google App Engine python - Self is not defined

  - by sdasdas

  I have a request that maps to this class ChatMsg It takes in 3 get variables, username, roomname, and msg. But it fails on this last line here. class ChatMsg(webapp.RequestHandler): # this is line 239 def get(self): username = urllib.unquote(self.request.get('username')) roomname = urllib.unquote(self.request.get('roomname')) # this is line 242 When it tries to assign roomname, it tells me: <type 'exceptions.NameError'>: name 'self' is not defined Traceback (most recent call last): File "/base/data/home/apps/chatboxes/1.341998073649951735/chatroom.py", line 239, in <module> class ChatMsg(webapp.RequestHandler): File "/base/data/home/apps/chatboxes/1.341998073649951735/chatroom.py", line 242, in ChatMsg roomname = urllib.unquote(self.request.get('roomname')) what the hell is going on to make self not defined

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• if (self = [super init]) vs. if ((self = [super init]))

  - by JOM

  Was just doing a code review and started to wonder: I thought if (self = [super init]) checks whether assigning return value of [super init] to variable self was successful or not (value of operation). Thus (self = nil) would actually be TRUE. I thought if ((self = [super init])) checks what is the value of self after assignment (value of variable). Thus ((self = nil)) would be FALSE. Which one is the correct way to use when initializing your own classes? Apple documentation uses the former one (for example here), which style I'm actually using now.

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• Is it possible to force the WCF test client to accept a self-signed certificate?

  - by Lawrence Johnston

  I have a WCF web service running in IIS 7 using a self-signed certificate (it's a proof of concept to make sure this is the route I want to go). It's required to use SSL. Is it possible to use the WCF Test Client to debug this service without needing a non-self-signed certificate? When I try I get this error: Error: Cannot obtain Metadata from https:///Service1.svc If this is a Windows (R) Communication Foundation service to which you have access, please check that you have enabled metadata publishing at the specified address. For help enabling metadata publishing, please refer to the MSDN documentation at http://go.microsoft.com/fwlink/?LinkId=65455.WS-Metadata Exchange Error URI: https:///Service1.svc Metadata contains a reference that cannot be resolved: 'https:///Service1.svc'. Could not establish trust relationship for the SSL/TLS secure channel with authority ''. The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel. The remote certificate is invalid according to the validation procedure.HTTP GET Error URI: https:///Service1.svc There was an error downloading 'https:///Service1.svc'. The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel. The remote certificate is invalid according to the validation procedure.

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• Reflect.Emit Dynamic Type Memory Blowup

  - by Firestrand

  Using C# 3.5 I am trying to generate dynamic types at runtime using reflection emit. I used the Dynamic Query Library sample from Microsoft to create a class generator. Everything works, my problem is that 100 generated types inflate the memory usage by approximately 25MB. This is a completely unacceptable memory profile as eventually I want to support having several hundred thousand types generated in memory. Memory profiling shows that the memory is apparently being held by various System.Reflection.Emit types and methods though I can't figure out why. I haven't found others talking about this problem so I am hoping someone in this community either knows what I am doing wrong or if this is expected behavior. Contrived Example below: using System; using System.Collections.Generic; using System.Text; using System.Reflection; using System.Reflection.Emit; namespace SmallRelfectExample { class Program { static void Main(string[] args) { int typeCount = 100; int propCount = 100; Random rand = new Random(); Type dynType = null; for (int i = 0; i < typeCount; i++) { List<DynamicProperty> dpl = new List<DynamicProperty>(propCount); for (int j = 0; j < propCount; j++) { dpl.Add(new DynamicProperty("Key" + rand.Next().ToString(), typeof(String))); } SlimClassFactory scf = new SlimClassFactory(); dynType = scf.CreateDynamicClass(dpl.ToArray(), i); //Optionally do something with the type here } Console.WriteLine("SmallRelfectExample: {0} Types generated.", typeCount); Console.ReadLine(); } } public class SlimClassFactory { private readonly ModuleBuilder module; public SlimClassFactory() { AssemblyName name = new AssemblyName("DynamicClasses"); AssemblyBuilder assembly = AppDomain.CurrentDomain.DefineDynamicAssembly(name, AssemblyBuilderAccess.Run); module = assembly.DefineDynamicModule("Module"); } public Type CreateDynamicClass(DynamicProperty[] properties, int Id) { string typeName = "DynamicClass" + Id.ToString(); TypeBuilder tb = module.DefineType(typeName, TypeAttributes.Class | TypeAttributes.Public, typeof(DynamicClass)); FieldInfo[] fields = GenerateProperties(tb, properties); GenerateEquals(tb, fields); GenerateGetHashCode(tb, fields); Type result = tb.CreateType(); return result; } static FieldInfo[] GenerateProperties(TypeBuilder tb, DynamicProperty[] properties) { FieldInfo[] fields = new FieldBuilder[properties.Length]; for (int i = 0; i < properties.Length; i++) { DynamicProperty dp = properties[i]; FieldBuilder fb = tb.DefineField("_" + dp.Name, dp.Type, FieldAttributes.Private); PropertyBuilder pb = tb.DefineProperty(dp.Name, PropertyAttributes.HasDefault, dp.Type, null); MethodBuilder mbGet = tb.DefineMethod("get_" + dp.Name, MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig, dp.Type, Type.EmptyTypes); ILGenerator genGet = mbGet.GetILGenerator(); genGet.Emit(OpCodes.Ldarg_0); genGet.Emit(OpCodes.Ldfld, fb); genGet.Emit(OpCodes.Ret); MethodBuilder mbSet = tb.DefineMethod("set_" + dp.Name, MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig, null, new Type[] { dp.Type }); ILGenerator genSet = mbSet.GetILGenerator(); genSet.Emit(OpCodes.Ldarg_0); genSet.Emit(OpCodes.Ldarg_1); genSet.Emit(OpCodes.Stfld, fb); genSet.Emit(OpCodes.Ret); pb.SetGetMethod(mbGet); pb.SetSetMethod(mbSet); fields[i] = fb; } return fields; } static void GenerateEquals(TypeBuilder tb, FieldInfo[] fields) { MethodBuilder mb = tb.DefineMethod("Equals", MethodAttributes.Public | MethodAttributes.ReuseSlot | MethodAttributes.Virtual | MethodAttributes.HideBySig, typeof(bool), new Type[] { typeof(object) }); ILGenerator gen = mb.GetILGenerator(); LocalBuilder other = gen.DeclareLocal(tb); Label next = gen.DefineLabel(); gen.Emit(OpCodes.Ldarg_1); gen.Emit(OpCodes.Isinst, tb); gen.Emit(OpCodes.Stloc, other); gen.Emit(OpCodes.Ldloc, other); gen.Emit(OpCodes.Brtrue_S, next); gen.Emit(OpCodes.Ldc_I4_0); gen.Emit(OpCodes.Ret); gen.MarkLabel(next); foreach (FieldInfo field in fields) { Type ft = field.FieldType; Type ct = typeof(EqualityComparer<>).MakeGenericType(ft); next = gen.DefineLabel(); gen.EmitCall(OpCodes.Call, ct.GetMethod("get_Default"), null); gen.Emit(OpCodes.Ldarg_0); gen.Emit(OpCodes.Ldfld, field); gen.Emit(OpCodes.Ldloc, other); gen.Emit(OpCodes.Ldfld, field); gen.EmitCall(OpCodes.Callvirt, ct.GetMethod("Equals", new Type[] { ft, ft }), null); gen.Emit(OpCodes.Brtrue_S, next); gen.Emit(OpCodes.Ldc_I4_0); gen.Emit(OpCodes.Ret); gen.MarkLabel(next); } gen.Emit(OpCodes.Ldc_I4_1); gen.Emit(OpCodes.Ret); } static void GenerateGetHashCode(TypeBuilder tb, FieldInfo[] fields) { MethodBuilder mb = tb.DefineMethod("GetHashCode", MethodAttributes.Public | MethodAttributes.ReuseSlot | MethodAttributes.Virtual | MethodAttributes.HideBySig, typeof(int), Type.EmptyTypes); ILGenerator gen = mb.GetILGenerator(); gen.Emit(OpCodes.Ldc_I4_0); foreach (FieldInfo field in fields) { Type ft = field.FieldType; Type ct = typeof(EqualityComparer<>).MakeGenericType(ft); gen.EmitCall(OpCodes.Call, ct.GetMethod("get_Default"), null); gen.Emit(OpCodes.Ldarg_0); gen.Emit(OpCodes.Ldfld, field); gen.EmitCall(OpCodes.Callvirt, ct.GetMethod("GetHashCode", new Type[] { ft }), null); gen.Emit(OpCodes.Xor); } gen.Emit(OpCodes.Ret); } } public abstract class DynamicClass { public override string ToString() { PropertyInfo[] props = GetType().GetProperties(BindingFlags.Instance | BindingFlags.Public); StringBuilder sb = new StringBuilder(); sb.Append("{"); for (int i = 0; i < props.Length; i++) { if (i > 0) sb.Append(", "); sb.Append(props[i].Name); sb.Append("="); sb.Append(props[i].GetValue(this, null)); } sb.Append("}"); return sb.ToString(); } } public class DynamicProperty { private readonly string name; private readonly Type type; public DynamicProperty(string name, Type type) { if (name == null) throw new ArgumentNullException("name"); if (type == null) throw new ArgumentNullException("type"); this.name = name; this.type = type; } public string Name { get { return name; } } public Type Type { get { return type; } } } }

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• Is it Possible to Use Constraints on Hierarchical Data in a Self-Referential Table?

  - by pbarney

  Suppose you have the following table, intended to represent hierarchical data: +--------+-------------+ | Field | Type | +--------+-------------+ | id | int(10) | | parent | int(10) | | name | varchar(45) | +--------+-------------+ The table is self-referential in that the parent_id refers to id. So you might have the following data: +----+--------+---------------+ | id | parent | name | +----+--------+---------------+ | 1 | 0 | fruit | | 2 | 0 | vegetable | | 3 | 1 | apple | | 4 | 1 | orange | | 5 | 3 | red delicious | | 6 | 3 | granny smith | | 7 | 3 | gala | +----+--------+---------------+ Using MySQL, I am trying to impose a (self-referential) foreign key constraint upon the data to cascade on update and prevent deletion of a record if it has any "children." So I used the following: CREATE TABLE `test`.`fruit` ( `id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT, `parent` INT(10) UNSIGNED, `name` VARCHAR(45) NOT NULL, PRIMARY KEY (`id`), CONSTRAINT `fk_parent` FOREIGN KEY (`parent`) REFERENCES `fruit` (`id`) ON UPDATE CASCADE ON DELETE RESTRICT ) ENGINE = InnoDB; From what I understand, this should fit my requirements. (And parent must default to null to allow insertions, correct?) The problem is, if I change the id of a record, it will not cascade: Cannot delete or update a parent row: a foreign key constraint fails (`test`.`fruit`, CONSTRAINT `fk_parent` FOREIGN KEY (`parent`) REFERENCES `fruit` (`id`) ON UPDATE CASCADE) What am I missing? Feel free to correct me if my terminology is screwed up... I'm new to constraints.

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• Play mp3 using Python, PyQt, and Phonon

  - by KeyboardInterrupt

  I been trying all day to figure out the Qt's Phonon library with Python. My long term goal is to see if I could get it to play a mms:// stream, but since I can't find an implementation of this done anywhere, I will figure that part out myself. (figured I'd put it out there if anyone knew more about this specifically, if not no big deal.) Anyway, I figured I'd work backwards from a working example I found online. This launches a file browser and will play the mp3 file specified. I wanted to strip out the file browser stuff and get it down to the essentials of executing the script and having it play an Mp3 file with a hardcoded path. I'm assuming my problem is a misunderstanding of setCurrentSource() and specifying the data types. (see: http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/phonon-mediasource.html#fileName) I'm keeping my question kind of broad because ANY help with understanding Phonon would be greatly appreciated. import sys from PyQt4.QtGui import QApplication, QMainWindow, QDirModel, QColumnView from PyQt4.QtGui import QFrame from PyQt4.QtCore import SIGNAL from PyQt4.phonon import Phonon class MainWindow(QMainWindow): m_model = QDirModel() def __init__(self): QMainWindow.__init__(self) self.m_fileView = QColumnView(self) self.m_media = None self.setCentralWidget(self.m_fileView) self.m_fileView.setModel(self.m_model) self.m_fileView.setFrameStyle(QFrame.NoFrame) self.connect(self.m_fileView, SIGNAL("updatePreviewWidget(const QModelIndex &)"), self.play) def play(self, index): self.delayedInit() self.m_media.setCurrentSource( Phonon.MediaSource(self.m_model.filePath(index))) self.m_media.play() def delayedInit(self): if not self.m_media: self.m_media = Phonon.MediaObject(self) audioOutput = Phonon.AudioOutput(Phonon.MusicCategory, self) Phonon.createPath(self.m_media, audioOutput) def main(): app = QApplication(sys.argv) QApplication.setApplicationName("Phonon Tutorial 2 (Python)") mw = MainWindow() mw.show() sys.exit(app.exec_()) if __name__ == '__main__': main()

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• Python Tkinter comparing PhotoImage objects

  - by Kyle Schmidt

  In a simple LightsOut game, when I click on a light I need to toggle the image on a button. I'm doing this with Tkinter, so I thought I'd just check and see what image is currently on the button (either 'on.gif' or 'off.gif') and set it to the other one, like this: def click(self,x,y): if self.buttons[x][y].image == self.on: self.buttons[x][y].config(image=self.off) self.buttons[x][y].image == self.off else: self.buttons[x][y].config(image=self.on) self.buttons[x][y].image == self.on This ends up always being True - I can turn a lgiht off, but never turn it back on. Did some research, realized that I should probably be using cmp: def click(self,x,y): if cmp(self.buttons[x][y].image,self.on) == 0: self.buttons[x][y].config(image=self.off) self.buttons[x][y].image == self.off else: self.buttons[x][y].config(image=self.on) self.buttons[x][y].image == self.on But that gave me the exact same result. Both self.on and self.off are PhotoImage objects. Aside from keeping a separate set of lists which tracks what type of light is in each position and redrawing them every click, is there a way to directly compare two PhotoImage objects like this?

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• PyGTK: Trouble with size of ScrolledWindow

  - by canavanin

  Hi everyone! I am using PyGTK and the gtk.Assistant. On one page I have placed a treeview (one column, just strings) in a gtk.ScrolledWindow (I wanted the vertical scrollbar, since the list contains about 35 items). Everything is working fine; the only thing that bugs me is that I have not been able to figure out from the documentation how to set the size of the scrolled window. Currently only three items are displayed at a time; I would like to set this number to 10 or so. Below is the code. As you can see I have tried using a gtk.Adjustment to influence the scrolled window's size, but as - once more - I have been incompetent at retrieving the required info from the documentation, I don't actually know what values should be put into there. self.page7 = gtk.VBox() # The gtk.Adjustment: page_size = gtk.Adjustment(lower=10, page_size=100) # just used some arbitrary numbers here >_< scrolled_win = gtk.ScrolledWindow(page_size) scrolled_win.set_policy(gtk.POLICY_AUTOMATIC, gtk.POLICY_AUTOMATIC) # only display scroll bars when required self.character_traits_treeview = gtk.TreeView() self.character_traits_treestore = gtk.TreeStore(str) self.character_traits_treeview.set_model(self.character_traits_treestore) tc = gtk.TreeViewColumn("Character traits") self.character_traits_treeview.append_column(tc) cr = gtk.CellRendererText() tc.pack_start(cr, True) tc.add_attribute(cr, "text", 0) self.character_trait_selection = self.character_traits_treeview.get_selection() self.character_trait_selection.connect('changed', self.check_number_of_character_trait_selections) self.character_trait_selection.set_mode(gtk.SELECTION_MULTIPLE) self.make_character_traits_treestore() # adding the treeview to the scrolled window: scrolled_win.add(self.character_traits_treeview) self.page7.pack_start(scrolled_win, False, False, 0) self.assistant.append_page(self.page7) self.assistant.set_page_title(self.page7, "Step 7: Select 2-3 character traits") self.assistant.set_page_type(self.page7, gtk.ASSISTANT_PAGE_CONTENT) self.assistant.set_page_complete(self.page7, False) def check_number_of_character_trait_selections(self, blah): # ... def make_character_traits_treestore(self): # ... I know I should RTFM, but as I can't make head or tail of it, and as further searching, too, has been to no avail, I'm just hoping that someone on here can give me a hint. Thanks a lot in advance! PS: Here are the links to: the gtk.ScrolledWindow documentation the gtk.Adjustment documentation

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• How can I change 'self.view' within a button method created outside of 'loadView'

  - by Scott

  Hey guys. So I am creating buttons dynamically within loadView. Each of these buttons is given an action using the @Selector method, such as : [button addTarget:self action:@selector(showCCView) forControlEvents:UIControlEventTouchUpInside]; Now that showCCView method is defined outside of loadView, where this above statement is located. The point of the method is to change the view currently on the screen (so set self.view = ccView). It gives me an error every time I try and access self.view outside of loadView, and even sometimes when I try and access it at random places within loadView, it just has been acting really weird. I tried to change it around so I wouldn't have to deal with this either. I had made a function + (void) showView: (UIView*) oldView: (UIView*) newView; but this didn't work out either because the @Selector was being real prissy about using it with a function that needed two parameters. Any help please? Here is my code: // // SiteOneController.m // InstantNavigator // // Created by dni on 2/22/10. // Copyright 2010 __MyCompanyName__. All rights reserved. // #import "SiteOneController.h" @implementation SiteOneController + (UIView*) ccContent { UIView *ccContent = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]]; ccContent.backgroundColor = [UIColor whiteColor]; [ccContent addSubview:[SiteOneController myNavBar1:@"Constitution Center Content"]]; return ccContent; } // Button Dimensions int a = 62; int b = 80; int c = 200; int d = 30; // NPSIN Green Color + (UIColor*)myColor1 { return [UIColor colorWithRed:0.0f/255.0f green:76.0f/255.0f blue:29.0f/255.0f alpha:1.0f]; } // Creates Nav Bar with default Green at top of screen with given String as title + (UINavigationBar*)myNavBar1: (NSString*)input { UIView *test = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]]; UINavigationBar *navBar = [[UINavigationBar alloc] initWithFrame:CGRectMake(0.0, 0.0, test.bounds.size.width, 45)]; navBar.tintColor = [SiteOneController myColor1]; UINavigationItem *navItem; navItem = [UINavigationItem alloc]; navItem.title = input; [navBar pushNavigationItem:navItem animated:false]; return navBar; } //-------------------------------------------------------------------------------------------// //-------------------------------------------------------------------------------------------// //-------------------------------------------------------------------------------------------// // Implement loadView to create a view hierarchy programmatically, without using a nib. - (void)loadView { //hard coded array of content for each site // CC NSMutableArray *allccContent = [[NSMutableArray alloc] init]; NSString *cc1 = @"House Model"; NSString *cc2 = @"James Dexter History"; [allccContent addObject: cc1]; [cc1 release]; [allccContent addObject: cc2]; [cc2 release]; // FC NSMutableArray *allfcContent = [[NSMutableArray alloc] init]; NSString *fc1 = @"Ghost House"; NSString *fc2 = @"Franklins Letters"; NSString *fc3 = @"Franklins Business"; [allfcContent addObject: fc1]; [fc1 release]; [allfcContent addObject: fc2]; [fc2 release]; [allfcContent addObject: fc3]; [fc3 release]; // PC NSMutableArray *allphContent = [[NSMutableArray alloc] init]; NSString *ph1 = @"Changing Occupancy"; NSString *ph2 = @"Sketches"; NSString *ph3 = @"Servant House"; NSString *ph4 = @"Monument"; NSString *ph5 = @"Virtual Model"; [allphContent addObject: ph1]; [ph1 release]; [allphContent addObject: ph2]; [ph2 release]; [allphContent addObject: ph3]; [ph3 release]; [allphContent addObject: ph4]; [ph4 release]; [allphContent addObject: ph5]; [ph5 release]; // Each content page's view //UIView *ccContent = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]]; UIView *fcContent = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]]; UIView *phContent = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]]; //ccContent.backgroundColor = [UIColor whiteColor]; fcContent.backgroundColor = [UIColor whiteColor]; phContent.backgroundColor = [UIColor whiteColor]; //[ccContent addSubview:[SiteOneController myNavBar1:@"Constitution Center Content"]]; [fcContent addSubview:[SiteOneController myNavBar1:@"Franklin Court Content"]]; [phContent addSubview:[SiteOneController myNavBar1:@"Presidents House Content"]]; //allocate the view self.view = [[UIView alloc] initWithFrame:[[UIScreen mainScreen] applicationFrame]]; //set the view's background color self.view.backgroundColor = [UIColor whiteColor]; [self.view addSubview:[SiteOneController myNavBar1:@"Sites"]]; NSMutableArray *sites = [[NSMutableArray alloc] init]; NSString *one = @"Constution Center"; NSString *two = @"Franklin Court"; NSString *three = @"Presidents House"; [sites addObject: one]; [one release]; [sites addObject: two]; [two release]; [sites addObject: three]; [three release]; NSString *ccName = @"Constitution Center"; NSString *fcName = @"Franklin Court"; NSString *element; int j = 0; for (element in sites) { UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom]; //setframe (where on screen) //separation is 15px past the width (45-30) button.frame = CGRectMake(a, b + (j*45), c, d); [button setTitle:element forState:UIControlStateNormal]; button.backgroundColor = [SiteOneController myColor1]; /*- (void) fooFirstInput:(NSString*) first secondInput:(NSString*) second { NSLog(@"Logs %@ then %@", first, second); } - (void) performMethodsViaSelectors { [self performSelector:@selector(fooNoInputs)]; [self performSelector:@selector(fooOneInput:) withObject:@"first"]; [self performSelector;@selector(fooFirstInput:secondInput:) withObject:@"first" withObject:@"second"];*/ //UIView *old = self.view; if (element == ccName) { [button addTarget:self action:@selector(showCCView) forControlEvents:UIControlEventTouchUpInside]; } else if (element == fcName) { } else { } [self.view addSubview: button]; j++; } } // This method show the content views for each of the sites. /*+ (void) showCCView { self.view = [SiteOneController ccContent]; }*/

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• Self Hosted WCF REST Service or Hosting WCF REST Service in Console Application

  n this article, I will show you How to create a REST based service, How to host a REST,based service in Console application and How to consume a REST Service at client.

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• Setting up a local AI server - easy with Solaris 11

  - by Stefan Hinker

  Many things are new in Solaris 11, Autoinstall is one of them.  If, like me, you've known Jumpstart for the last 2 centuries or so, you'll have to start from scratch.  Well, almost, as the concepts are similar, and it's not all that difficult.  Just new. I wanted to have an AI server that I could use for demo purposes, on the train if need be.  That answers the question of hardware requirements: portable.  But let's start at the beginning. First, you need an OS image, of course.  In the new world of Solaris 11, it is now called a repository.  The original can be downloaded from the Solaris 11 page at Oracle.   What you want is the "Oracle Solaris 11 11/11 Repository Image", which comes in two parts that can be combined using cat.  MD5 checksums for these (and all other downloads from that page) are available closer to the top of the page. With that, building the repository is quick and simple: # zfs create -o mountpoint=/export/repo rpool/ai/repo # zfs create rpool/ai/repo/s11 # mount -o ro -F hsfs /tmp/sol-11-1111-repo-full.iso /mnt # rsync -aP /mnt/repo /export/repo/s11 # umount /mnt # pkgrepo rebuild -s /export/repo/sol11/repo # zfs snapshot rpool/ai/repo/sol11@fcs # pkgrepo info -s /export/repo/sol11/repo PUBLISHER PACKAGES STATUS UPDATED solaris 4292 online 2012-03-12T20:47:15.378639Z That's all there's to it.  Let's make a snapshot, just to be on the safe side.  You never know when one will come in handy.  To use this repository, you could just add it as a file-based publisher: # pkg set-publisher -g file:///export/repo/sol11/repo solaris In case I'd want to access this repository through a (virtual) network, i'll now quickly activate the repository-service: # svccfg -s application/pkg/server \ setprop pkg/inst_root=/export/repo/sol11/repo # svccfg -s application/pkg/server setprop pkg/readonly=true # svcadm refresh application/pkg/server # svcadm enable application/pkg/server That's all you need - now point your browser to http://localhost/ to view your beautiful repository-server. Step 1 is done.  All of this, by the way, is nicely documented in the README file that's contained in the repository image. Of course, we already have updates to the original release.  You can find them in MOS in the Oracle Solaris 11 Support Repository Updates (SRU) Index.  You can simply add these to your existing repository or create separate repositories for each SRU.  The individual SRUs are self-sufficient and incremental - SRU4 includes all updates from SRU2 and SRU3.  With ZFS, you can also get both: A full repository with all updates and at the same time incremental ones up to each of the updates: # mount -o ro -F hsfs /tmp/sol-11-1111-sru4-05-incr-repo.iso /mnt # pkgrecv -s /mnt/repo -d /export/repo/sol11/repo '*' # umount /mnt # pkgrepo rebuild -s /export/repo/sol11/repo # zfs snapshot rpool/ai/repo/sol11@sru4 # zfs set snapdir=visible rpool/ai/repo/sol11 # svcadm restart svc:/application/pkg/server:default The normal repository is now updated to SRU4.  Thanks to the ZFS snapshots, there is also a valid repository of Solaris 11 11/11 without the update located at /export/repo/sol11/.zfs/snapshot/fcs . If you like, you can also create another repository service for each update, running on a separate port. But now lets continue with the AI server.  Just a little bit of reading in the dokumentation makes it clear that we will need to run a DHCP server for this.  Since I already have one active (for my SunRay installation) and since it's a good idea to have these kinds of services separate anyway, I decided to create this in a Zone.  So, let's create one first: # zfs create -o mountpoint=/export/install rpool/ai/install # zfs create -o mountpoint=/zones rpool/zones # zonecfg -z ai-server zonecfg:ai-server> create create: Using system default template 'SYSdefault' zonecfg:ai-server> set zonepath=/zones/ai-server zonecfg:ai-server> add dataset zonecfg:ai-server:dataset> set name=rpool/ai/install zonecfg:ai-server:dataset> set alias=install zonecfg:ai-server:dataset> end zonecfg:ai-server> commit zonecfg:ai-server> exit # zoneadm -z ai-server install # zoneadm -z ai-server boot ; zlogin -C ai-server Give it a hostname and IP address at first boot, and there's the Zone.  For a publisher for Solaris packages, it will be bound to the "System Publisher" from the Global Zone.  The /export/install filesystem, of course, is intended to be used by the AI server.  Let's configure it now: #zlogin ai-server root@ai-server:~# pkg install install/installadm root@ai-server:~# installadm create-service -n x86-fcs -a i386 \ -s pkg://solaris/install-image/[email protected],5.11-0.175.0.0.0.2.1482 \ -d /export/install/fcs -i 192.168.2.20 -c 3 With that, the core AI server is already done.  What happened here?  First, I installed the AI server software.  IPS makes that nice and easy.  If necessary, it'll also pull in the required DHCP-Server and anything else that might be missing.  Watch out for that DHCP server software.  In Solaris 11, there are two different versions.  There's the one you might know from Solaris 10 and earlier, and then there's a new one from ISC.  The latter is the one we need for AI.  The SMF service names of both are very similar.  The "old" one is "svc:/network/dhcp-server:default". The ISC-server comes with several SMF-services. We at least need "svc:/network/dhcp/server:ipv4".  The command "installadm create-service" creates the installation-service. It's called "x86-fcs", serves the "i386" architecture and gets its boot image from the repository of the system publisher, using version 5.11,5.11-0.175.0.0.0.2.1482, which is Solaris 11 11/11.  (The option "-a i386" in this example is optional, since the installserver itself runs on a x86 machine.) The boot-environment for clients is created in /export/install/fcs and the DHCP-server is configured for 3 IP-addresses starting at 192.168.2.20.  This configuration is stored in a very human readable form in /etc/inet/dhcpd4.conf.  An AI-service for SPARC systems could be created in the very same way, using "-a sparc" as the architecture option. Now we would be ready to register and install the first client.  It would be installed with the default "solaris-large-server" using the publisher "http://pkg.oracle.com/solaris/release" and would query it's configuration interactively at first boot.  This makes it very clear that an AI-server is really only a boot-server.  The true source of packets to install can be different.  Since I don't like these defaults for my demo setup, I did some extra config work for my clients. The configuration of a client is controlled by manifests and profiles.  The manifest controls which packets are installed and how the filesystems are layed out.  In that, it's very much like the old "rules.ok" file in Jumpstart.  Profiles contain additional configuration like root passwords, primary user account, IP addresses, keyboard layout etc.  Hence, profiles are very similar to the old sysid.cfg file. The easiest way to get your hands on a manifest is to ask the AI server we just created to give us it's default one.  Then modify that to our liking and give it back to the installserver to use: root@ai-server:~# mkdir -p /export/install/configs/manifests root@ai-server:~# cd /export/install/configs/manifests root@ai-server:~# installadm export -n x86-fcs -m orig_default \ -o orig_default.xml root@ai-server:~# cp orig_default.xml s11-fcs.small.local.xml root@ai-server:~# vi s11-fcs.small.local.xml root@ai-server:~# more s11-fcs.small.local.xml <!DOCTYPE auto_install SYSTEM "file:///usr/share/install/ai.dtd.1"> <auto_install> <ai_instance name="S11 Small fcs local"> <target> <logical> <zpool name="rpool" is_root="true"> <filesystem name="export" mountpoint="/export"/> <filesystem name="export/home"/> <be name="solaris"/> </zpool> </logical> </target> <software type="IPS"> <destination> <image> <!-- Specify locales to install --> <facet set="false">facet.locale.*</facet> <facet set="true">facet.locale.de</facet> <facet set="true">facet.locale.de_DE</facet> <facet set="true">facet.locale.en</facet> <facet set="true">facet.locale.en_US</facet> </image> </destination> <source> <publisher name="solaris"> <origin name="http://192.168.2.12/"/> </publisher> </source> <!-- By default the latest build available, in the specified IPS repository, is installed. If another build is required, the build number has to be appended to the 'entire' package in the following form: <name>pkg:/[email protected]#</name> --> <software_data action="install"> <name>pkg:/[email protected],5.11-0.175.0.0.0.2.0</name> <name>pkg:/group/system/solaris-small-server</name> </software_data> </software> </ai_instance> </auto_install> root@ai-server:~# installadm create-manifest -n x86-fcs -d \ -f ./s11-fcs.small.local.xml root@ai-server:~# installadm list -m -n x86-fcs Manifest Status Criteria -------- ------ -------- S11 Small fcs local Default None orig_default Inactive None The major points in this new manifest are: Install "solaris-small-server" Install a few locales less than the default.  I'm not that fluid in French or Japanese... Use my own package service as publisher, running on IP address 192.168.2.12 Install the initial release of Solaris 11:  pkg:/[email protected],5.11-0.175.0.0.0.2.0 Using a similar approach, I'll create a default profile interactively and use it as a template for a few customized building blocks, each defining a part of the overall system configuration.  The modular approach makes it easy to configure numerous clients later on: root@ai-server:~# mkdir -p /export/install/configs/profiles root@ai-server:~# cd /export/install/configs/profiles root@ai-server:~# sysconfig create-profile -o default.xml root@ai-server:~# cp default.xml general.xml; cp default.xml mars.xml root@ai-server:~# cp default.xml user.xml root@ai-server:~# vi general.xml mars.xml user.xml root@ai-server:~# more general.xml mars.xml user.xml :::::::::::::: general.xml :::::::::::::: <!DOCTYPE service_bundle SYSTEM "/usr/share/lib/xml/dtd/service_bundle.dtd.1"> <service_bundle type="profile" name="sysconfig"> <service version="1" type="service" name="system/timezone"> <instance enabled="true" name="default"> <property_group type="application" name="timezone"> <propval type="astring" name="localtime" value="Europe/Berlin"/> </property_group> </instance> </service> <service version="1" type="service" name="system/environment"> <instance enabled="true" name="init"> <property_group type="application" name="environment"> <propval type="astring" name="LANG" value="C"/> </property_group> </instance> </service> <service version="1" type="service" name="system/keymap"> <instance enabled="true" name="default"> <property_group type="system" name="keymap"> <propval type="astring" name="layout" value="US-English"/> </property_group> </instance> </service> <service version="1" type="service" name="system/console-login"> <instance enabled="true" name="default"> <property_group type="application" name="ttymon"> <propval type="astring" name="terminal_type" value="vt100"/> </property_group> </instance> </service> <service version="1" type="service" name="network/physical"> <instance enabled="true" name="default"> <property_group type="application" name="netcfg"> <propval type="astring" name="active_ncp" value="DefaultFixed"/> </property_group> </instance> </service> <service version="1" type="service" name="system/name-service/switch"> <property_group type="application" name="config"> <propval type="astring" name="default" value="files"/> <propval type="astring" name="host" value="files dns"/> <propval type="astring" name="printer" value="user files"/> </property_group> <instance enabled="true" name="default"/> </service> <service version="1" type="service" name="system/name-service/cache"> <instance enabled="true" name="default"/> </service> <service version="1" type="service" name="network/dns/client"> <property_group type="application" name="config"> <property type="net_address" name="nameserver"> <net_address_list> <value_node value="192.168.2.1"/> </net_address_list> </property> </property_group> <instance enabled="true" name="default"/> </service> </service_bundle> :::::::::::::: mars.xml :::::::::::::: <!DOCTYPE service_bundle SYSTEM "/usr/share/lib/xml/dtd/service_bundle.dtd.1"> <service_bundle type="profile" name="sysconfig"> <service version="1" type="service" name="network/install"> <instance enabled="true" name="default"> <property_group type="application" name="install_ipv4_interface"> <propval type="astring" name="address_type" value="static"/> <propval type="net_address_v4" name="static_address" value="192.168.2.100/24"/> <propval type="astring" name="name" value="net0/v4"/> <propval type="net_address_v4" name="default_route" value="192.168.2.1"/> </property_group> <property_group type="application" name="install_ipv6_interface"> <propval type="astring" name="stateful" value="yes"/> <propval type="astring" name="stateless" value="yes"/> <propval type="astring" name="address_type" value="addrconf"/> <propval type="astring" name="name" value="net0/v6"/> </property_group> </instance> </service> <service version="1" type="service" name="system/identity"> <instance enabled="true" name="node"> <property_group type="application" name="config"> <propval type="astring" name="nodename" value="mars"/> </property_group> </instance> </service> </service_bundle> :::::::::::::: user.xml :::::::::::::: <!DOCTYPE service_bundle SYSTEM "/usr/share/lib/xml/dtd/service_bundle.dtd.1"> <service_bundle type="profile" name="sysconfig"> <service version="1" type="service" name="system/config-user"> <instance enabled="true" name="default"> <property_group type="application" name="root_account"> <propval type="astring" name="login" value="root"/> <propval type="astring" name="password" value="noIWillNotTellYouMyPasswordNotEvenEncrypted"/> <propval type="astring" name="type" value="role"/> </property_group> <property_group type="application" name="user_account"> <propval type="astring" name="login" value="stefan"/> <propval type="astring" name="password" value="noIWillNotTellYouMyPasswordNotEvenEncrypted"/> <propval type="astring" name="type" value="normal"/> <propval type="astring" name="description" value="Stefan Hinker"/> <propval type="count" name="uid" value="12345"/> <propval type="count" name="gid" value="10"/> <propval type="astring" name="shell" value="/usr/bin/bash"/> <propval type="astring" name="roles" value="root"/> <propval type="astring" name="profiles" value="System Administrator"/> <propval type="astring" name="sudoers" value="ALL=(ALL) ALL"/> </property_group> </instance> </service> </service_bundle> root@ai-server:~# installadm create-profile -n x86-fcs -f general.xml root@ai-server:~# installadm create-profile -n x86-fcs -f user.xml root@ai-server:~# installadm create-profile -n x86-fcs -f mars.xml \ -c ipv4=192.168.2.100 root@ai-server:~# installadm list -p Service Name Profile ------------ ------- x86-fcs general.xml mars.xml user.xml root@ai-server:~# installadm list -n x86-fcs -p Profile Criteria ------- -------- general.xml None mars.xml ipv4 = 192.168.2.100 user.xml None Here's the idea behind these files: "general.xml" contains settings valid for all my clients.  Stuff like DNS servers, for example, which in my case will always be the same. "user.xml" only contains user definitions.  That is, a root password and a primary user.Both of these profiles will be valid for all clients (for now). "mars.xml" defines network settings for an individual client.  This profile is associated with an IP-Address.  For this to work, I'll have to tweak the DHCP-settings in the next step: root@ai-server:~# installadm create-client -e 08:00:27:AA:3D:B1 -n x86-fcs root@ai-server:~# vi /etc/inet/dhcpd4.conf root@ai-server:~# tail -5 /etc/inet/dhcpd4.conf host 080027AA3DB1 { hardware ethernet 08:00:27:AA:3D:B1; fixed-address 192.168.2.100; filename "01080027AA3DB1"; } This completes the client preparations.  I manually added the IP-Address for mars to /etc/inet/dhcpd4.conf.  This is needed for the "mars.xml" profile.  Disabling arbitrary DHCP-replies will shut up this DHCP server, making my life in a shared environment a lot more peaceful ;-)Now, I of course want this installation to be completely hands-off.  For this to work, I'll need to modify the grub boot menu for this client slightly.  You can find it in /etc/netboot.  "installadm create-client" will create a new boot menu for every client, identified by the client's MAC address.  The template for this can be found in a subdirectory with the name of the install service, /etc/netboot/x86-fcs in our case.  If you don't want to change this manually for every client, modify that template to your liking instead. root@ai-server:~# cd /etc/netboot root@ai-server:~# cp menu.lst.01080027AA3DB1 menu.lst.01080027AA3DB1.org root@ai-server:~# vi menu.lst.01080027AA3DB1 root@ai-server:~# diff menu.lst.01080027AA3DB1 menu.lst.01080027AA3DB1.org 1,2c1,2 < default=1 < timeout=10 --- > default=0 > timeout=30 root@ai-server:~# more menu.lst.01080027AA3DB1 default=1 timeout=10 min_mem64=0 title Oracle Solaris 11 11/11 Text Installer and command line kernel$ /x86-fcs/platform/i86pc/kernel/$ISADIR/unix -B install_media=htt p://$serverIP:5555//export/install/fcs,install_service=x86-fcs,install_svc_addre ss=$serverIP:5555 module$ /x86-fcs/platform/i86pc/$ISADIR/boot_archive title Oracle Solaris 11 11/11 Automated Install kernel$ /x86-fcs/platform/i86pc/kernel/$ISADIR/unix -B install=true,inst all_media=http://$serverIP:5555//export/install/fcs,install_service=x86-fcs,inst all_svc_address=$serverIP:5555,livemode=text module$ /x86-fcs/platform/i86pc/$ISADIR/boot_archive Now just boot the client off the network using PXE-boot.  For my demo purposes, that's a client from VirtualBox, of course.  That's all there's to it.  And despite the fact that this blog entry is a little longer - that wasn't that hard now, was it?

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• SQL SERVER – DMV – sys.dm_os_wait_stats Explanation – Wait Type – Day 3 of 28

  - by pinaldave

  The key Dynamic Management View (DMV) that helps us to understand wait stats is sys.dm_os_wait_stats; this DMV gives us all the information that we need to know regarding wait stats. However, the interpretation is left to us. This is a challenge as understanding wait stats can often be quite tricky. Anyway, we will cover few wait stats in one of the future articles. Today we will go over the basic understanding of the DMV. The Official Book OnLine Reference for DMV is over here: sys.dm_os_wait_stats. I suggest you all to refer this for all the accuracy. Following is a statement from the online book: “Specific types of wait times during query execution can indicate bottlenecks or stall points within the query. Similarly, high wait times, or wait counts server wide can indicate bottlenecks or hot spots in interaction query interactions within the server instance.” This is the statement which has inspired me to write this series. Let us first run the following statement from DMV. SELECT * FROM sys.dm_os_wait_stats ORDER BY wait_time_ms DESC GO Above statement will show us few of the columns. Here it is quick explanation of each of the column. wait_type – this is the name of the wait type. There can be three different kinds of wait types – resource, queue and external. waiting_tasks_count – this incremental counter is a good indication of frequent the wait is happening. If this number is very high, it is good indication for us to investigate that particular wait type. It is quite possible that the wait time is considerably low, but the frequency of the wait is much high. wait_time_ms – this is total wait accumulated for any type of wait. This is the total wait time and includes singal_wait_time_ms. max_wait_time_ms – this indicates the maximum wait type ever occurred for that particular wait type. Using this, one can estimate the intensity of the wait type in past. Again, it is not necessary that this max wait time will occur every time; so do not over invest yourself here. signal_wait_time_ms – this is the wait time when thread is marked as runnable and it gets to the running state. If the runnable queue is very long, you will find that this wait time becomes high. Additionally, please note that this DMV does not show current wait type or wait stats. This is cumulative view of the all the wait stats since server (instance) restarted or wait stats have been cleared. In future blog post, we will also cover two more DMVs which can be helpful to identify wait-related issues. ?sys.dm_os_waiting_tasks sys.dm_exec_requests Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL DMV, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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• How I understood monads, part 1/2: sleepless and self-loathing in Seattle

  - by Latest Microsoft Blogs

  For some time now, I had been noticing some interest for monads, mostly in the form of unintelligible (to me) blog posts and comments saying “oh, yeah, that’s a monad” about random stuff as if it were absolutely obvious and if I didn’t know what they Read More......(read more)

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• How I understood monads, part 1/2: sleepless and self-loathing in Seattle

  For some time now, I had been noticing some interest for monads, mostly in the form of unintelligible (to me) blog posts and comments saying oh, yeah, thats a monad about random stuff as if it were absolutely obvious and if I didnt know what they were talking about, I was probably an uneducated idiot, ignorant about the simplest and most fundamental concepts of functional programming. Fair enough, I am pretty much exactly that. Being the kind of guy who can spend eight years in college just to...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• How I understood monads, part 1/2: sleepless and self-loathing in Seattle

  - by Bertrand Le Roy

  For some time now, I had been noticing some interest for monads, mostly in the form of unintelligible (to me) blog posts and comments saying “oh, yeah, that’s a monad” about random stuff as if it were absolutely obvious and if I didn’t know what they were talking about, I was probably an uneducated idiot, ignorant about the simplest and most fundamental concepts of functional programming. Fair enough, I am pretty much exactly that. Being the kind of guy who can spend eight years in college just to understand a few interesting concepts about the universe, I had to check it out and try to understand monads so that I too can say “oh, yeah, that’s a monad”. Man, was I hit hard in the face with the limitations of my own abstract thinking abilities. All the articles I could find about the subject seemed to be vaguely understandable at first but very quickly overloaded the very few concept slots I have available in my brain. They also seemed to be consistently using arcane notation that I was entirely unfamiliar with. It finally all clicked together one Friday afternoon during the team’s beer symposium when Louis was patient enough to break it down for me in a language I could understand (C#). I don’t know if being intoxicated helped. Feel free to read this with or without a drink in hand. So here it is in a nutshell: a monad allows you to manipulate stuff in interesting ways. Oh, OK, you might say. Yeah. Exactly. Let’s start with a trivial case: public static class Trivial { public static TResult Execute<T, TResult>( this T argument, Func<T, TResult> operation) { return operation(argument); } } This is not a monad. I removed most concepts here to start with something very simple. There is only one concept here: the idea of executing an operation on an object. This is of course trivial and it would actually be simpler to just apply that operation directly on the object. But please bear with me, this is our first baby step. Here’s how you use that thing: "some string" .Execute(s => s + " processed by trivial proto-monad.") .Execute(s => s + " And it's chainable!"); What we’re doing here is analogous to having an assembly chain in a factory: you can feed it raw material (the string here) and a number of machines that each implement a step in the manufacturing process and you can start building stuff. The Trivial class here represents the empty assembly chain, the conveyor belt if you will, but it doesn’t care what kind of raw material gets in, what gets out or what each machine is doing. It is pure process. A real monad will need a couple of additional concepts. Let’s say the conveyor belt needs the material to be processed to be contained in standardized boxes, just so that it can safely and efficiently be transported from machine to machine or so that tracking information can be attached to it. Each machine knows how to treat raw material or partly processed material, but it doesn’t know how to treat the boxes so the conveyor belt will have to extract the material from the box before feeding it into each machine, and it will have to box it back afterwards. This conveyor belt with boxes is essentially what a monad is. It has one method to box stuff, one to extract stuff from its box and one to feed stuff into a machine. So let’s reformulate the previous example but this time with the boxes, which will do nothing for the moment except containing stuff. public class Identity<T> { public Identity(T value) { Value = value; } public T Value { get; private set;} public static Identity<T> Unit(T value) { return new Identity<T>(value); } public static Identity<U> Bind<U>( Identity<T> argument, Func<T, Identity<U>> operation) { return operation(argument.Value); } } Now this is a true to the definition Monad, including the weird naming of the methods. It is the simplest monad, called the identity monad and of course it does nothing useful. Here’s how you use it: Identity<string>.Bind( Identity<string>.Unit("some string"), s => Identity<string>.Unit( s + " was processed by identity monad.")).Value That of course is seriously ugly. Note that the operation is responsible for re-boxing its result. That is a part of strict monads that I don’t quite get and I’ll take the liberty to lift that strange constraint in the next examples. To make this more readable and easier to use, let’s build a few extension methods: public static class IdentityExtensions { public static Identity<T> ToIdentity<T>(this T value) { return new Identity<T>(value); } public static Identity<U> Bind<T, U>( this Identity<T> argument, Func<T, U> operation) { return operation(argument.Value).ToIdentity(); } } With those, we can rewrite our code as follows: "some string".ToIdentity() .Bind(s => s + " was processed by monad extensions.") .Bind(s => s + " And it's chainable...") .Value; This is considerably simpler but still retains the qualities of a monad. But it is still pointless. Let’s look at a more useful example, the state monad, which is basically a monad where the boxes have a label. It’s useful to perform operations on arbitrary objects that have been enriched with an attached state object. public class Stateful<TValue, TState> { public Stateful(TValue value, TState state) { Value = value; State = state; } public TValue Value { get; private set; } public TState State { get; set; } } public static class StateExtensions { public static Stateful<TValue, TState> ToStateful<TValue, TState>( this TValue value, TState state) { return new Stateful<TValue, TState>(value, state); } public static Stateful<TResult, TState> Execute<TValue, TState, TResult>( this Stateful<TValue, TState> argument, Func<TValue, TResult> operation) { return operation(argument.Value) .ToStateful(argument.State); } } You can get a stateful version of any object by calling the ToStateful extension method, passing the state object in. You can then execute ordinary operations on the values while retaining the state: var statefulInt = 3.ToStateful("This is the state"); var processedStatefulInt = statefulInt .Execute(i => ++i) .Execute(i => i * 10) .Execute(i => i + 2); Console.WriteLine("Value: {0}; state: {1}", processedStatefulInt.Value, processedStatefulInt.State); This monad differs from the identity by enriching the boxes. There is another way to give value to the monad, which is to enrich the processing. An example of that is the writer monad, which can be typically used to log the operations that are being performed by the monad. Of course, the richest monads enrich both the boxes and the processing. That’s all for today. I hope with this you won’t have to go through the same process that I did to understand monads and that you haven’t gone into concept overload like I did. Next time, we’ll examine some examples that you already know but we will shine the monadic light, hopefully illuminating them in a whole new way. Realizing that this pattern is actually in many places but mostly unnoticed is what will enable the truly casual “oh, yes, that’s a monad” comments. Here’s the code for this article: http://weblogs.asp.net/blogs/bleroy/Samples/Monads.zip The Wikipedia article on monads: http://en.wikipedia.org/wiki/Monads_in_functional_programming This article was invaluable for me in understanding how to express the canonical monads in C# (interesting Linq stuff in there): http://blogs.msdn.com/b/wesdyer/archive/2008/01/11/the-marvels-of-monads.aspx

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• Bullet physics in python and pygame

  - by Pomg

  I am programming a 2D sidescroller in python and pygame and am having trouble making a bullet go farther than just farther than the player. The bullet travels straight to the ground after i fire it. How, in python code using pygame do I make the bullet go farther. If you need code, here is the method that handles the bullet firing: self.xv += math.sin(math.radians(self.angle)) * self.attrs['speed'] self.yv += math.cos(math.radians(self.angle)) * self.attrs['speed'] self.rect.left += self.xv self.rect.top += self.yv

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• Generic and type safe I/O model in any language

  - by Eduardo León

  I am looking for an I/O model, in any programming language, that is generic and type safe. By genericity, I mean there should not be separate functions for performing the same operations on different devices (read_file, read_socket, read_terminal). Instead, a single read operation works on all read-able devices, a single write operation works on all write-able devices, and so on. By type safety, I mean operations that do not make sense should not even be expressible in first place. Using the read operation on a non-read-able device ought to cause a type error at compile time, similarly for using the write operation on a non-write-able device, and so on. Is there any generic and type safe I/O model?

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