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• How do you keep application logic separate from UI when UI components have built-in functionality?

  - by Al C

  I know it's important to keep user interface code separated from domain code--the application is easier to understand, maintain, change, and (sometimes) isolate bugs. But here's my mental block ... Delphi comes with components with methods that do what I want, e.g., a RichText Memo component lets me work with rich text. Other components, like TMS's string grid not only do what I want, but I paid extra for the functionality. These features put the R in RAD. It seems illogical to write my own classes to do things somebody else has already done for me. It's reinventing the wheel [ever tried working directly with rich text? :-) ] But if I use the functionality built into components like these, then I will end up with lots of intermingled UI and domain code--I'll have a form with most of my code built into its event handlers. How do you deal with this issue? ... Or, if I want to continue using the code others have already written for me, how would you suggest I deal with the issue?

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• Is it poor design to create objects that only execute code during the constructor?

  - by Curtix

  In my design I am using objects that evaluate a data record. The constructor is called with the data record and type of evaluation as parameters and then the constructor calls all of the object's code necessary to evaluate the record. This includes using the type of evaluation to find additional parameter-like data in a text file. There are in the neighborhood of 250 unique evaluation types that use the same or similar code and unique parameters coming from the text file. Some of these evaluations use different code so I benefit a lot from this model because I can use inheritance and polymorphism. Once the object is created there isn't any need to execute additional code on the object (at least for now) and it is used more like a struct; its kept on a list and 3 properties are used later. I think this design is the easiest to understand, code, and read. A logical alternative I guess would be using functions that return score structs, but you can't inherit from methods so it would make it kind of sloppy imo. I am using vb.net and these classes will be used in an asp.net web app as well as in a distributed app. thanks for your input

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• Recursive powerof-function, see if you can solve it

  - by Jonas B

  First of all, this is not schoolwork - just my curiousity as I for some reason can't get my head around it and solve it. I come up with these stupid things all the time and it annoys the hell out of me when I cant solve them. Code example is in C# but solution doesn't have to be in any particular programming-language. long powerofnum(short num, long powerof) { return powerofnum2(num, powerof, powerof); } long powerofnum2(short num, long powerof, long holder) { if (num == 1) return powerof; else { return powerof = powerofnum2(num - 1, holder * powerof, holder); } } As you can see I have two methods. I call for powerofnum(value, powerofvalue) which then calls the next method with the powerofvalue also in a third parameter as a placeholder so it remembers the original powerof value through the recursion. What I want to accomplish is to do this with only one method. I know I could just declare a variable in the first method with the powerof value to remember it and then iterate from 0 to value of num. But as this is a theoretical question I want it done recursively. I could also in the first method just take a third parameter called whatever to store the value just like I do in the second method that is called by the first, but that looks really stupid. Why should you have to write what seems like the same parameter twice? Rules explained in short: no iteration scope-specific variables only only one method Anyhow, I'd appreciate a clean solution. Good luck :)

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• Recursive Iterators

  - by soandos

  I am having some trouble making an iterator that can traverse the following type of data structure. I have a class called Expression, which has one data member, a List<object>. This list can have any number of children, and some of those children might be other Expression objects. I want to traverse this structure, and print out every non-list object (but I do want to print out the elements of the list of course), but before entering a list, I want to return "begin nest" and after I just exited a list, I want to return "end nest". I was able to do this if I ignored the class wherever possible, and just had List<object> objects with List<object> items if I wanted a subExpression, but I would rather do away with this, and instead have an Expressions as the sublists (it would make it easier to do operations on the object. I am aware that I could use extension methods on the List<object> but it would not be appropriate (who wants an Evaluate method on their list that takes no arguments?). The code that I used to generate the origonal iterator (that works) is: public IEnumerator GetEnumerator(){ return theIterator(expr).GetEnumerator(); } private IEnumerable theIterator(object root) { if ((root is List<object>)){ yield return " begin nest "; foreach (var item in (List<object>)root){ foreach (var item2 in theIterator(item)){ yield return item2; } } yield return " end nest "; } else yield return root; } A type swap of List<object> for expression did not work, and lead to a stackOverflow error. How should the iterator be implemented? Update: Here is the swapped code: public IEnumerator GetEnumerator() { return this.GetEnumerator(); } private IEnumerable theIterator(object root) { if ((root is Expression)) { yield return " begin nest "; foreach (var item in (Expression)root) { foreach (var item2 in theIterator(item)) yield return item2; } yield return " end nest "; } else yield return root; }

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• Javascript Closures, Callbacks, This and That

  - by nazbot

  I am having some trouble getting a callback function to work. Here is my code: SomeObject.prototype.refreshData = function() { var read_obj = new SomeAjaxCall("read_some_data", { }, this.readSuccess, this.readFail); } SomeObject.prototype.readSuccess = function(response) { this.data = response; this.someList = []; for (var i = 0; i < this.data.length; i++) { var systemData = this.data[i]; var system = new SomeSystem(systemData); this.someList.push(system); } this.refreshList(); } Basically SomeAjaxCall is making an ajax request for data. If it works we use the callback 'this.readSuccess' and if it fails 'this.readFail'. I have figured out that 'this' in the SomeObject.readSuccess is the global this (aka the window object) because my callbacks are being called as functions and not member methods. My understanding is that I need to use closures to keep the 'this' around, however, I have not been able to get this to work. If someone is able show me what I should be doing I would appreciate it greatly. I am still wrapping my head around how closures work and specifically how they would work in this situation. Thanks!

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• Ensuring quality of your software and code

  - by Filip Ekberg

  When I usually write code I follow some guidelines to ensure that my code has a certain standard and I as any other developer try to ensure that my code and software is of quality. Try to focus on the programming and not the understanding of the domain or any other pre-programming steps. These are the following steps I live by: Writing unit tests Make it fail ( no code ) Make it Work ( working code ) Analysing abstraction Extracting methods Exteract interfaces Refactoring In addition to the above which is a part of refactoring, I also try to refactor the code with good tools such as ReSharper, CodeRush or others. The question; What is the next step? Commenting the code is trivial and shouldn't even have to be mentioned, but updated comments and xml-comments where it's needed / everywhere is something that I try to have. But all the above helps he ensure that other developers might understand my code, that the code has some sort of quality and follows naming standards. It does however not ensure any product quality. I am looking for tools for post-development quality ensurance, such as profilers and how one would use these tools to increase product quality.

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• "Finding" an object instance of a known class?

  - by Sean C

  My first post here (anywhere for that matter!), re. Cocoa/Obj-C (I'm NOT up to speed on either, please be patient!). I hope I haven't missed the answer already, I did try to find it. I'm an old-school procedural dog (haven't done any programming since the mid 80's, so I probably just can't even learn new tricks), but OOP has my head spinning! My question is: is there any means at all to "discover/find/identify" an instance of an object of a known class, given that some OTHER unknown process instantiated it? eg. somthing that would accomplish this scenario: (id) anObj = [someTarget getMostRecentInstanceOf:[aKnownClass class]]; for that matter, "getAnyInstance" or "getAllInstances" might do the trick too. Background: I'm trying to write a plugin for a commercial application, so much of the heavy lifting is being done by the app, behind the scenes. I have the SDK & header files, I know what class the object is, and what method I need to call (it has only instance methods), I just can't identify the object for targetting. I've spent untold hours and days going over Apples documentation, tutorials and lots of example/sample code on the web (including here at Stack Overflow), and come up empty. Seems that everything requires a known target object to work, and I just don't have one. Since I may not be expressing my problem as clearly as needed, I've put up a web page, with diagram & working sample pages to illustrate: http://www.nulltime.com/svtest/index.html Any help or guidance will be appreciated! Thanks.

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• WCF Multiple contracts with duplicate method names

  - by haxelit

  Hello, I have a service with multiple contracts like so. [ServiceContract] public partial interface IBusinessFunctionDAO { [OperationContract] BusinessFunction GetBusinessFunction(Int32 businessFunctionRefID); [OperationContract] IEnumerable<Project> GetProjects(Int32 businessFunctionRefID); } [ServiceContract] public partial interface IBusinessUnitDAO { [OperationContract] BusinessUnit GetBusinessUnit(Int32 businessUnitRefID); [OperationContract] IEnumerable<Project> GetProjects(Int32 businessUnitRefID); } I then explicitly implemented each one of the interfaces like so. public class TrackingTool : IBusinessFunctionDAO, IBusinessUnitDAO { BusinessFunction IBusinessFunctionDAO.GetBusinessFunction(Int32 businessFunctionRefID) { // implementation } IEnumerable<Project> IBusinessFunctionDAO.GetProjects(Int32 businessFunctionRefID) { // implementation } BusinessUnit IBusinessUnitDAO.GetBusinessUnit(Int32 businessUnitRefID) { // implementation } IEnumerable<Project> IBusinessUnitDAO.GetProjects(Int32 businessUnitRefID) { // implementation } } As you can see I have two GetProjects(int) methods, but each one is implemented explicitly so this compiles just fine and is perfectly valid. The problem arises when I actually start this as a service. It gives me an error staying that TrackingTool already contains a definition GetProject. While it is true, it is part of a different service contract. Does WCF not distinguish between service contracts when generating the method names ? Is there a way to get it to distinguish between the service contracts ? My App.Config looks like this <service name="TrackingTool"> <endpoint address="BusinessUnit" contract="IBusinessUnitDAO" /> <endpoint address="BusinessFunction" contract="IBusinessFunctionDAO" /> </service> Any help would be appreciated. Thanks, Raul

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• Change a finder method w/ parameters to an association

  - by Sai Emrys

  How do I turn this into a has_one association? (Possibly has_one + a named scope for size.) class User < ActiveRecord::Base has_many :assets, :foreign_key => 'creator_id' def avatar_asset size = :thumb # The LIKE is because it might be a .jpg, .png, or .gif. # More efficient methods that can handle that are OK. ;) self.assets.find :first, :conditions => ["thumbnail = '#{size}' and filename LIKE ?", self.login + "_#{size}.%"] end end EDIT: Cuing from AnalogHole on Freenode #rubyonrails, we can do this: has_many :assets, :foreign_key => 'creator_id' do def avatar size = :thumb find :first, :conditions => ["thumbnail = ? and filename LIKE ?", size.to_s, proxy_owner.login + "_#{size}.%"] end end ... which is fairly cool, and makes syntax a bit better at least. However, this still doesn't behave as well as I would like. Particularly, it doesn't allow for further nice find chaining (such that it doesn't execute this find until it's gotten all its conditions). More importantly, it doesn't allow for use in an :include. Ideally I want to do something like this: PostsController def show post = Post.get_cache(params[:id]) { Post.find(params[:id], :include => {:comments => {:users => {:avatar_asset => :thumb}} } ... end ... so that I can cache the assets together with the post. Or cache them at all, really - e.g. get_cache(user_id){User.find(user_id, :include => :avatar_assets)} would be a good first pass. This doesn't actually work (self == User), but is correct in spirit: has_many :avatar_assets, :foreign_key => 'creator_id', :class_name => 'Asset', :conditions => ["filename LIKE ?", self.login + "_%"] (Also posted on Refactor My Code.)

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• Custom UITableView headerView disappears after memory warning

  - by psychotik

  I have a UITableViewController. I create a custom headerView for it's tableView in the loadView method like so: (void)loadView { [super loadView]; UIView* containerView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, width, height * 2 )]; containerView.tag = 'cont'; containerView.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin | UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleTopMargin; UIButton* button = [UIButton buttonWithType:UIButtonTypeCustom]; button.frame = CGRectMake(padding, height, width, height); ... //configure UIButton and events UIImageView* imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"image.png"] highlightedImage:[UIImage imageNamed:@"highlight.png"]]; imageView.frame = CGRectMake(0, 0, width, height ); ... //configure UIImageView [containerView addSubview:button]; [containerView addSubview:imageView]; self.tableView.tableHeaderView = containerView; [imageView release]; [containerView release]; } None of the other methods (viewDidLoad/Unload, etc) are overloaded. This controller is hosted in a tab. When I switch to another tab and simulate a memory warning, and then come back to this tab, my UITableView is missing my custon header. All the rows/section are visible as I would expect. Putting a BP in the loadView code above, I see it being invoked when I switch back to the tab after the memory warning, and yet I can't actually see the header. Any ideas about what I'm missing here? EDIT: This happens on the device and the simulator. On the device, I just let a memory warning occur by opening a bunch of different apps while mine is in the background.

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• NSProgressIndicator woes - perhaps my NSView subclass?

  - by mootymoots

  Hi All I have created a basic application, created a subclassed NSView, and added it as a custom view in interface builder. All works ok. However certain things do not work correctly, which makes me wonder if my NSView is subclassed correctly? Specifically, when using an NSProgressIndicator, I can use startAnimating: and stopAnimating on an indeterminate, but if I try and do anything with a determinate with incrementBy it does nothing. Even if I set the default value of the determinate NSProgressIndicator to 50.0, it appears when the app is launched at 0.0, despite looking good in IB. My NSProgressIndicator is hooked up correctly as an IBOutlet, I can tell it to hide etc, just can't get it to animate at all. However, I also have other issues that make me think that this problem is actually my NSView subclass (such as Quick Look not firing). In my subclass I've simply overridden the initWithFrame: and drawRect methods, calling their [super]. As I said, I've then placed this as a custom view in interface builder and changed it to MyCustomView. All works fine mostly...? Am I subclassing this incorrectly, or not doing something in interface builder correctly? I seem to be missing some small thing?!

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• Why does this threading approach not work?

  - by Tomas Lycken

  I have a wierd problem with threading in an ASP.NET application. For some reason, when I run the code in the request thread, everything works as expected. But when I run it in a separate thread, nothing happens. This is verified by calling the below handler with the three flags "on", "off" and "larma" respectively - in the two first cases everything works, but in the latter nothing happens. What am I doing wrong here? In the web project I have a generic handler with the following code: If task = "on" Then Alarm.StartaLarm(personId) context.Response.Write("Larmet är PÅ") ElseIf task = "off" Then Alarm.StoppaLarm(personId) context.Response.Write("Larmet är AV") ElseIf task = "larma" Then Alarm.Larma(personId) context.Response.Write("Larmar... (stängs av automagiskt)") Else context.Response.Write("inget hände - task: " & task) End If The Alarm class has the following methods: Private Shared Sub Larma_Thread(ByVal personId As Integer) StartaLarm(personId) Thread.Sleep(1000 * 30) StoppaLarm(personId) End Sub Public Shared Sub StartaLarm(ByVal personId As Integer) SandSMS(True, personId) End Sub Public Shared Sub StoppaLarm(ByVal personId As Integer) SandSMS(False, personId) End Sub Public Shared Sub SandSMS(ByVal setOn As Boolean, ByVal personId As Integer) ... End Sub

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• Reference to the Main Form whilst trying to Serialize objects in C#

  - by Paul Matthews

  I have a button on my main form which calls a method to serialize some objects to disk. I am trying to add these objects to an ArrayList and then serialize them using a BinaryFormatter and a FileStream. public void SerializeGAToDisk(string GenAlgName) { // Let's make a list that includes all the objects we // need to store a GA instance ArrayList GAContents = new ArrayList(); GAContents.Add(GenAlgInstances[GenAlgName]); // Structure and info for a GA GAContents.Add(RunningGAs[GenAlgName]); // There may be several running GA's using (FileStream fStream = new FileStream(GenAlgName + ".ga", FileMode.Create, FileAccess.Write, FileShare.None)) { BinaryFormatter binFormat = new BinaryFormatter(); binFormat.Serialize(fStream, GAContents); } } When running the above code I get the following exception: System.Runtime.Serialization.SerializationException was unhandled Message=Type 'WindowsFormsApplication1.Form1' in Assembly 'GeneticAlgApp, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' is not marked as serializable. So that means that somewhere in the objects I'm trying to save there must be a reference to the main form. The only possible references I can see are 3 delegates which all point to methods in the main form code. Do delegates get serialized as well? I can't seem to apply the [NonSerialized] attribute to them. Is there anything else I might be missing? Even better, is there a quick method to find the reference(s) that are causing the problem?

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• Codeigniter - change url at method call

  - by NemoPS

  I was wondering if the following can be done in codeigniter. Let's assume I have a file, called Post.php, used to manage posts in an admin interface. It has several methods, such as index (lists all posts), add, update, delete... Now, I access the add method, so that the url becomes /posts/add And I add some data. I click "save" to add the new post. It calls the same method with an if statement like "if "this-input-post('addnew')"" is passed, call the model, add it to the database Here follows the problem: If everything worked fine, it goes to the index with the list of all posts, and displays a confirmation BUT No the url would still be posts/add, since I called the function like $this-index() after verifying data was added. I cannot redirect it to "posts/" since in that case no confirmation message would be shown! So my question is: can i call a method from anther one in the same class, and have the url set to that method (/posts/index instead of /posts/add)? It's kinda confusing, but i hope i gave you enough info to spot the problem Cheers!

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• Should conditional expressions go inside or outside of classes?

  - by Rupert

  It seems that often I will want to execute some methods from a Class when I call it and choosing which function will depend on some condition. This leads me to write classes like in Case 1 because it allows me to rapidly include their functionality. The alternative would be Case 2 which can take a lot of time if there is a lot of code and also means more code being written twice when I drop the Class into different pages. Having said that, Case 1 feels very wrong for some reason that I can't quite put my finger on. I haven't really seen any classes written like this, I suppose. Is there anything wrong with writing classes like in Case 1 or is Case 2 superior? Or is there a better way? What the advantages and disadvantages of each? Case 1 class Foo { public function __construct($bar) { if($bar = 'action1') $this->method1(); else if($bar = 'action2') $this->method2(); else $this->method1(); } public function method1() { } public function method2() { } } $bar = 'action1' $foo = new Foo($bar); Case 2 class Foo { public function __construct() { } public function method1() { } public function method2() { } } $foo = new Foo; $bar = 'action1'; if($bar == 'action1') $foo->method1(); else if($bar == 'action2') $foo->method2(); else $foo->method1();

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• What are possible/good ways to prototype iPhone applications?

  - by Ted Johnson

  This is intentionally left broad. If you wanted to show users what iPhone/mobile applications could to for them. The more interactive the better, but it must be quick to build as you can't code up every idea. Let us assume real-time games are out of scope. Throw out ideas or state which approach would be best. Here are some of my ideas, what are yours? Hack a app that loads mostly web or image content, but has hyperlinks to get around in. This would mean static data. Build screens which look great but can only be navigated in a story board type fashion. Load the web version or equivalent on the iPhone and say: now image the buttons and navigation is better. A paper based prototype. Flash or video walk through running on the phone. String existing iPhone apps and web pages together with minimal glue just to convey the idea. Can anyone share prototyping methods for other mobile devices? Ex: The palm prototype was just a block of wood and note pad that was carried around.

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• Multiple exports with MEF does some really heinous stuff -- why, and why is it allowed?

  - by Dave

  I have an interesting situation where I need to do something like this: [Export[typeof(ICandy1)] [Export[typeof(ICandy2)] public class Candy : ICandy2 { ... } where public interface ICandy1 { ... } public interface ICandy2 : ICandy1 { ... } I couldn't find any posts anywhere regarding using multiple [Export] attributes, so I figured, what the hell, might as well try it. At first glance, it actually seemed to work. I have a couple of methods that call into both interfaces of a Candy instance, and it was fine. However, as I started to test the app, I saw that the behavior wasn't right, and when looking at the Output window, I saw that I was getting tons of COMExceptions. I couldn't track down where they were all coming from, but they always occurred when a worker thread was sleeping. I figured that it had to be from the main thread, then, but didn't know how to debug this at all. Nothing should have been going on in the GUI, and I disabled my DispatchTimers just in case -- same thing. Even more strange than the COMExceptions was the really, really erratic behavior when stepping through code. About 30% of the time, when I single stepped, it would pop out of the method, or it would single step over two lines of code! Totally weird stuff that I am not used to seeing. The only thing that changed between working and non-working code was the introduction of MEF through my plugin loading code. So as a test, I changed my plugin assembly to only export one interface, and I hardcoded everything in the app that relied on the other (now not-implemented) interface. And now the COMExceptions are gone, and the weird debugging behavior is gone. Is this something people here have seen before? If MEF is not expected to allow a class to Export multiple interfaces, then shouldn't a CompositionException get raised when composing the parts? Can anyone explain why MEF would cause these weird problems???

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• Different approaches for finding users within Active Directory

  - by EvilDr

  I'm a newbie to AD programming, but after a couple of weeks of research have found the following three ways to search for users in Active Directory using the account name as the search parameter: Option 1 - FindByIdentity Dim ctx As New PrincipalContext(ContextType.Domain, Environment.MachineName) Dim u As UserPrincipal = UserPrincipal.FindByIdentity(ctx, IdentityType.SamAccountName, "MYDOMAIN\Administrator") If u Is Nothing Then Trace.Warn("No user found.") Else Trace.Warn("Name=" & u.Name) Trace.Warn("DisplayName=" & u.DisplayName) Trace.Warn("DistinguishedName=" & u.DistinguishedName) Trace.Warn("EmployeeId=" & u.EmployeeId) Trace.Warn("EmailAddress=" & u.EmailAddress) End If Option 2 - DirectorySearcher Dim connPath As String = "LDAP://" & Environment.MachineName Dim de As New DirectoryEntry(connPath) Dim ds As New DirectorySearcher(de) ds.Filter = String.Format("(&(objectClass=user)(anr={0}))", Split(User.Identity.Name, "\")(1)) ds.PropertiesToLoad.Add("name") ds.PropertiesToLoad.Add("displayName") ds.PropertiesToLoad.Add("distinguishedName") ds.PropertiesToLoad.Add("employeeId") ds.PropertiesToLoad.Add("mail") Dim src As SearchResult = ds.FindOne() If src Is Nothing Then Trace.Warn("No user found.") Else For Each propertyKey As String In src.Properties.PropertyNames Dim valueCollection As ResultPropertyValueCollection = src.Properties(propertyKey) For Each propertyValue As Object In valueCollection Trace.Warn(propertyKey & "=" & propertyValue.ToString) Next Next End If Option 3 - PrincipalSearcher Dim ctx2 As New PrincipalContext(ContextType.Domain, Environment.MachineName) Dim sp As New UserPrincipal(ctx2) sp.SamAccountName = "MYDOMAIN\Administrator" Dim s As New PrincipalSearcher s.QueryFilter = sp Dim p2 As UserPrincipal = s.FindOne() If p2 Is Nothing Then Trace.Warn("No user found.") Else Trace.Warn(p2.Name) Trace.Warn(p2.DisplayName) Trace.Warn(p2.DistinguishedName) Trace.Warn(p2.EmployeeId) Trace.Warn(p2.EmailAddress) End If All three of these methods return the same results, but I was wondering if any particular method is better or worse than the others? Option 1 or 3 seem to be the best as they provide strongly-typed property names, but I might be wrong? My overall objective is to find a single user within AD based on the user principal value passed via the web browser when using Windows Authentication on a site (e.g. "MYDOMAIN\MyUserAccountName")

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• Does F# documentation have a way to search for functions by their types?

  - by Nathan Sanders

  Say I want to know if F# has a library function of type ('T -> bool) -> 'T list -> int ie, something that counts how many items of a list that a function returns true for. (or returns the index of the first item that returns true) I used to use the big list at the MSR site for F# before the documentation on MSDN was ready. I could just search the page for the above text because the types were listed. But now the MSDN documentation only lists types on the individual pages--the module page is a mush of descriptive text. Google kinda-sorta works, but it can't help with // compatible interfaces ('T -> bool) -> Seq<'T> -> int // argument-swaps Seq<'T> -> ('T -> bool) -> int // type-variable names ('a -> bool) -> Seq<'a> -> int // wrappers ('a -> bool) -> 'a list -> option<int> // uncurried versions ('T -> bool) * 'T list -> int // .NET generic syntax ('T -> bool) -> List<'T> -> int // methods List<'T> member : ('T -> bool) -> int Haskell has a standalone program for this called Hoogle. Does F# have an equivalent, like Fing or something?

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• Python: why does this code take forever (infinite loop?)

  - by Rosarch

  I'm developing an app in Google App Engine. One of my methods is taking never completing, which makes me think it's caught in an infinite loop. I've stared at it, but can't figure it out. Disclaimer: I'm using http://code.google.com/p/gaeunitlink text to run my tests. Perhaps it's acting oddly? This is the problematic function: def _traverseForwards(course, c_levels): ''' Looks forwards in the dependency graph ''' result = {'nodes': [], 'arcs': []} if c_levels == 0: return result model_arc_tails_with_course = set(_getListArcTailsWithCourse(course)) q_arc_heads = DependencyArcHead.all() for model_arc_head in q_arc_heads: for model_arc_tail in model_arc_tails_with_course: if model_arc_tail.key() in model_arc_head.tails: result['nodes'].append(model_arc_head.sink) result['arcs'].append(_makeArc(course, model_arc_head.sink)) # rec_result = _traverseForwards(model_arc_head.sink, c_levels - 1) # _extendResult(result, rec_result) return result Originally, I thought it might be a recursion error, but I commented out the recursion and the problem persists. If this function is called with c_levels = 0, it runs fine. The models it references: class Course(db.Model): dept_code = db.StringProperty() number = db.IntegerProperty() title = db.StringProperty() raw_pre_reqs = db.StringProperty(multiline=True) original_description = db.StringProperty() def getPreReqs(self): return pickle.loads(str(self.raw_pre_reqs)) def __repr__(self): return "%s %s: %s" % (self.dept_code, self.number, self.title) class DependencyArcTail(db.Model): ''' A list of courses that is a pre-req for something else ''' courses = db.ListProperty(db.Key) def equals(self, arcTail): for this_course in self.courses: if not (this_course in arcTail.courses): return False for other_course in arcTail.courses: if not (other_course in self.courses): return False return True class DependencyArcHead(db.Model): ''' Maintains a course, and a list of tails with that course as their sink ''' sink = db.ReferenceProperty() tails = db.ListProperty(db.Key) Utility functions it references: def _makeArc(source, sink): return {'source': source, 'sink': sink} def _getListArcTailsWithCourse(course): ''' returns a LIST, not SET there may be duplicate entries ''' q_arc_heads = DependencyArcHead.all() result = [] for arc_head in q_arc_heads: for key_arc_tail in arc_head.tails: model_arc_tail = db.get(key_arc_tail) if course.key() in model_arc_tail.courses: result.append(model_arc_tail) return result Am I missing something pretty obvious here, or is GAEUnit acting up?

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• What's the most efficient way to load data from a file to a collection on-demand?

  - by Dan

  I'm working on a java project that will allows users to parse multiple files with potentially thousands of lines. The information parsed will be stored in different objects, which then will be added to a collection. Since the GUI won't require to load ALL these objects at once and keep them in memory, I'm looking for an efficient way to load/unload data from files, so that data is only loaded into the collection when a user requests it. I'm just evaluation options right now. I've also thought of the case where, after loading a subset of the data into the collection, and presenting it on the GUI, the best way to reload the previously observed data. Re-run the parser/Populate collection/Populate GUI? or probably find a way to keep the collection into memory, or serialize/deserialize the collection itself? I know that loading/unloading subsets of data can get tricky if some sort of data filtering is performed. Let's say that I filter on ID, so my new subset will contain data from two previous analyzed subsets. This would be no problem is I keep a master copy of the whole data in memory. I've read that google-collections are good and efficient when handling big amounts of data, and offer methods that simplify lots of things so this might offer an alternative to allow me to keep the collection in memory. This is just general talking. The question on what collection to use is a separate and complex thing. Do you know what's the general recommendation on this type of task? I'd like to hear what you've done with similar scenarios. I can provide more specifics if needed.

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• How do I send data between two computers over the internet

  - by Johan

  I have been struggling with this for the entire day now, I hope somebody can help me with this. My problem is fairly simple: I wish to transfer data (mostly simple commands) from one PC to another over the internet. I have been able to achieve this using sockets in Java when both computers are connected to my home router. I then connected both computers to the internet using two different mobile phones and attempted to transmit the data again. I used the mobile phones as this provides a direct route to the internet and if I use my router I have to set up port forwarding, at least, that is how I understand it. I think the problem lies in the method that I set up the client socket. I used: Socket kkSocket = new Socket(ipAddress, 3333); where ipAddress is the IP address of the computer running the server. I got the IP address by right-clicking on the connection, status, support. Is that the correct IP address to use or where can I obtain the address of the server? Also, is it possible to get a fixed name for my computer that I can use instead of entering the IP address, as this changes every time I connect to the internet using my mobile phone? Alternatively, are there better methods to solving my problem such as using http, and if so, where can I find more information about this? Thanks!

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• Organizing a String based on maxlength of each field

  - by pringlesinn

  I've made a program that makes my life easier by reading a class and creating methods like these below: //Ferramentas Parâmetros acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Pesquisa", "ppaParametrosList", null, TipoAcessoBean.TELA)); acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Gravar", "ppaParametrosHome", "persist", TipoAcessoBean.ACAO)); acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Atualizar Dados", "ppaParametrosHome", "update", TipoAcessoBean.ACAO)); acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Leitura", "ppaParametrosHome", "find", TipoAcessoBean.ACAO)); acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Excluir", "ppaParametrosHome", "remove", TipoAcessoBean.ACAO)); Don't worry about the language. It won't make it harder to understand what I need to make. I want to organize it to be shown like this: //Ferramentas Parâmetros acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Pesquisa" , "ppaParametrosList", null , TipoAcessoBean.TELA)); acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Gravar" , "ppaParametrosHome", "persist", TipoAcessoBean.ACAO)); acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Atualizar Dados", "ppaParametrosHome", "update" , TipoAcessoBean.ACAO)); acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Leitura" , "ppaParametrosHome", "find" , TipoAcessoBean.ACAO)); acessos.add(new AcessoBean("Ferramentas", "Parâmetros", "Parâmetros", "Excluir" , "ppaParametrosHome", "remove" , TipoAcessoBean.ACAO)); I'm reading the whole class with Scanner, but once I read, I save only the things I want in a Collection containing this things above. How can I make a method to complete with blank to make it organized?

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• protect form hijacking hack

  - by Karem

  Yes hello today I discovered a hack for my site. When you write a msg on a users wall (in my communitysite) it runs a ajax call, to insert the msg to the db and will then on success slide down and show it. Works fine with no problem. So I was rethinking alittle, I am using POST methods for this and if it was GET method you could easily do ?msg=haxmsg&usr=12345679. But what could you do to come around the POST method? I made a new html document, made a form and on action i set "site.com/insertwall.php" (the file that normally are being used in ajax), i made some input fields with names exactly like i am doing with the ajaxcall (msg, uID (userid), BuID (by userid) ) and made a submit button. I know I have a page_protect() function on which requires you to login and if you arent you will be header to index.php. So i logged in (started session on my site.com) and then I pressed on this submit button. And then wops I saw on my site that it has made a new message. I was like wow, was it so easy to hijack POST method i thought maybe it was little more secure or something. I would like to know what could I do to prevent this hijacking? As i wouldnt even want to know what real hackers could do with this "hole". The page_protect secures that the sessions are from the same http user agent and so, and this works fine (tried to run the form without logging in, and it just headers me to startpage) but yea wouldnt take long time to figure out to log in first and then run it. Any advices are appreciated alot. I would like to keep my ajax calls most secure as possible and all of them are running on the POST method. What could I do to the insertwall.php, to check that it comes from the server or something.. Thank you

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• When should EntityManagerFactory instance be created/opened ?

  - by masato-san

  Ok, I read bunch of articles/examples how to write Entity Manager Factory in singleton. One of them easiest for me to understand a bit: http://javanotepad.blogspot.com/2007/05/jpa-entitymanagerfactory-in-web.html I learned that EntityManagerFactory (EMF) should only be created once preferably in application scope. And also make sure to close the EMF once it's used (?) So I wrote EMF helper class for business methods to use: public class EmProvider { private static final String DB_PU = "KogaAlphaPU"; public static final boolean DEBUG = true; private static final EmProvider singleton = new EmProvider(); private EntityManagerFactory emf; private EmProvider() {} public static EmProvider getInstance() { return singleton; } public EntityManagerFactory getEntityManagerFactory() { if(emf == null) { emf = Persistence.createEntityManagerFactory(DB_PU); } if(DEBUG) { System.out.println("factory created on: " + new Date()); } return emf; } public void closeEmf() { if(emf.isOpen() || emf != null) { emf.close(); } emf = null; if(DEBUG) { System.out.println("EMF closed at: " + new Date()); } } }//end class And my method using EmProvider: public String foo() { EntityManager em = null; List<Object[]> out = null; try { em = EmProvider.getInstance().getEntityManagerFactory().createEntityManager(); Query query = em.createNativeQuery(JPQL_JOIN); //just some random query out = query.getResultList(); } catch(Exception e) { //handle error.... } finally { if(em != null) { em.close(); //make sure to close EntityManager } } I made sure to close EntityManager (em) within method level as suggested. But when should EntityManagerFactory be closed then? And why EMF has to be singleton so bad??? I read about concurrency issues but as I am not experienced multi-thread-grammer, I can't really be clear on this idea.

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