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  • Populating JavaScript Array from JSP List

    - by tkeE2036
    Ok so perhaps someone can help me with a problem I'm trying to solve. Essentially I have a JSP page which gets a list of Country objects (from the method referenceData() from a Spring Portlet SimpleFormController, not entirely relevant but just mentioning in case it is). Each Country object has a Set of province objects and each province and country have a name field: public class Country { private String name; private Set<Province> provinces; //Getters and setters } public class Province { private String name; //Getters and setters } Now I have two drop down menus in my JSP for countries and provinces and I want to filter the provinces by country. I've been following this tutorial/guide to make a chain select in JavaScript. Now I need a dynamic way to create the JavaScript array from my content. And before anyone mentions AJAX this is out of the question since our project uses portlets and we'd like to stay away from using frameworks like DWR or creating a servlet. Here is the JavaScript/JSP I have so far but it is not populating the Array with anything: var countries = new Array(); <c:forEach items="${countryList}" var="country" varStatus="status"> countries[status.index] = new Array(); countries[status.index]['country'] = ${country.name}; countries[status.index]['provinces'] = [ <c:forEach items="${country.provinces}" var="province" varStatus="provinceStatus"> '${province.name}' <c:if test="${!provinceStatus.last}"> , </c:if> </c:forEach> ]; </c:forEach> Does anyone know how to create an JavaScript array in JSP in the case above or what the 'best-practice' would be considered in this case? Thanks in advance!

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  • Hooking thread exit

    - by mackenir
    Is there a way for me to hook the exit of managed threads (i.e. run some code on a thread, just before it exits?) I've developed a mechanism for hooking thread exit that works for some threads. Step 1: develop a 'hook' STA COM class that takes a callback function and calls it in its destructor. Step 2: create a ThreadStatic instance of this object on the thread I want to hook, and pass the object a managed delegate converted to an unmanaged function pointer. The delegate then gets called on thread exit (since the CLR calls IUnknown::Release on all STA COM RCWs as part of thread exit). This mechanism works on, for example, worker threads that I create in code using the Thread class. However, it doesn't seem to work for the application's main thread (be it a console or windows app). The 'hook' COM object seems to be deleted too late in the shutdown process and the attempt to call the delegate fails. (The reason I want to implement this facility is so I can run some native COM code on the exiting thread that works with STA COM objects that were created on the thread, before it's 'too late' (i.e. before the thread has exited, and it's no longer possible to work with STA COM objects on that thread.))

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  • Spy++ for PowerBuilder applications

    - by Frerich Raabe
    Hi, I'm trying to write a tool which lets me inspect the state of a PowerBuilder-based application. What I'm thinking of is something like Spy++ (or, even nicer, 'Snoop' as it exists for .NET applications) which lets me inspect the object tree (and properties of objects) of some PowerBuilder-based GUI. I did the same for ordinary (MFC-based) applications as well as .NET applications already, but unfortunately I never developed an application in PowerBuilder myself, so I'm generally thinking about two problems at this point: Is there some API (preferably in Java or C/C++) available which lets one traverse the tree of visual objects of a PowerBuilder application? I read up a bit on the PowerBuilder Native Interface system, but it seems that this is meant to write PowerBuilder extensions in C/C++ which can then be called from the PowerBuilder script language, right? If there is some API available - maybe PowerBuilder applications even expose some sort of IPC-enabled API which lets me inspect the state of a PowerBuilder object hierarchy without being within the process of the PowerBuilder application? Maybe there's an automation interface available, or something COM-based - or maybe something else? Right now, my impression is that probably need to inject a DLL into the process of the PowerBuilder application and then gain access to the running PowerBuilder VM so that I can query it for the object tree. Some sort of IPC mechanism will then let me transport this information out of the PowerBuilder application's process. Does anybody have some experience with this or can shed some light on whether anybody tried to do this already? Best regards, Frerich

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  • Generic Dictionary and generating a hashcode for multi-part key

    - by Andrew
    I have an object that has a multi-part key and I am struggling to find a suitable way override GetHashCode. An example of what the class looks like is. public class wibble{ public int keypart1 {get; set;} public int keypart2 {get; set;} public int keypart3 {get; set;} public int keypart4 {get; set;} public int keypart5 {get; set;} public int keypart6 {get; set;} public int keypart7 {get; set;} public single value {get; set;} } Note in just about every instance of the class no more than 2 or 3 of the keyparts would have a value greater than 0. Any ideas on how best to generate a unique hashcode in this situation? I have also been playing around with creating a key that is not unique, but spreads the objects evenly between the dictionaries buckets and then storing objects with matched hashes in a List< or LinkedList< or SortedList<. Any thoughts on this?

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  • Django model operating on a queryset

    - by jmoz
    I'm new to Django and somewhat to Python as well. I'm trying to find the idiomatic way to loop over a queryset and set a variable on each model. Basically my model depends on a value from an api, and a model method must multiply one of it's attribs by this api value to get an up-to-date correct value. At the moment I am doing it in the view and it works, but I'm not sure it's the correct way to achieve what I want. I have to replicate this looping elsewhere. Is there a way I can encapsulate the looping logic into a queryset method so it can be used in multiple places? I have this atm (I am using django-rest-framework): class FooViewSet(viewsets.ModelViewSet): model = Foo serializer_class = FooSerializer bar = # some call to an api def get_queryset(self): # Dynamically set the bar variable on each instance! foos = Foo.objects.filter(baz__pk=1).order_by('date') for item in foos: item.needs_bar = self.bar return items I would think something like so would be better: def get_queryset(self): bar = # some call to an api # Dynamically set the bar variable on each instance! return Foo.objects.filter(baz__pk=1).order_by('date').set_bar(bar) I'm thinking the api hit should be in the controller and then injected to instances of the model, but I'm not sure how you do this. I've been looking around querysets and managers but still can't figure it out nor decided if it's the best method to achieve what I want. Can anyone suggest the correct way to model this with django? Thanks.

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  • Deriving an HTMLElement Object from jQuery Object

    - by Jasconius
    I'm doing a fairly exhaustive series of DOM manipulations where a few elements (specifically form elements) have some events. I am dynamically creating (actually cloning from a source element) several boxes and assigning a change() event to them. The change event executes, and within the context of the event, "this" is the HTML Element Object. What I need to do at this point however is determine a contact for this HTML Element Object. I have these objects stored already as jQuery entities in assorted arrays, but obviously [HTMLElement Object] != [Object Object] And the trick is that I cannot cast $(this) and make a valid comparison since that would create a new object and the pointer would be different. So... I've been banging my head against this for a while. In the past I've been able to circumvent this problem by doing an innerHTML comparison, but in this case the objects I am comparing are 100% identical, just there's lots of them. Therefore I need a solid comparison. This would be easy if I could somehow derive the HTMLElement object from my originating jQuery object. Thoughts, other ideas? Help. :(

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  • Unit testing JSON output module, best practices

    - by Banang
    I am currently working on a module that takes one of our business objects and returns a json representation of that object to the caller. Due to limitations in our environment I am unable to use any existing json writer, so I have written my own, which is then used by the business object writer to serialize my objects. The json writer is tested in a way similar to this @Test public void writeEmptyArrayTest() { String expected = "[ ]"; writer.array().endArray(); assertEquals(expected, writer.toString()); } which is only manageable because of the small output each instruction produces, even though I keep feeling there must be a better way. The problem I am now facing is writing tests for the object writer module, where the output is much larger and much less manageable. The risk of spelling mistakes in the expected strings mucking up my tests seem too great, and writing code in this fashion seems both silly and unmanageable in a long term perspective. I keep feeling like I want to write tests to ensure that my tests are behaving correctly, and this feeling worries me. Therefore, is there a better way of doing this? Surely there must be? Does anyone know of any good literature in regard to this specific case (doesn't have to be json, but you know what I mean)? Grateful for all help.

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  • Does GC guarantee that cleared References are enqueued to ReferenceQueue in topological order?

    - by Dimitris Andreou
    Say there are two objects, A and B, and there is a pointer A.x --> B, and we create, say, WeakReferences to both A and B, with an associated ReferenceQueue. Assume that both A and B become unreachable. Intuitively B cannot be considered unreachable before A is. In such a case, do we somehow get a guarantee that the respective references will be enqueued in the intuitive (topological when there are no cycles) order in the ReferenceQueue? I.e. ref(A) before ref(B). I don't know - what if the GC marked a bunch of objects as unreachable, and then enqueued them in no particular order? I was reviewing Finalizer.java of guava, seeing this snippet: private void cleanUp(Reference<?> reference) throws ShutDown { ... if (reference == frqReference) { /* * The client no longer has a reference to the * FinalizableReferenceQueue. We can stop. */ throw new ShutDown(); } frqReference is a PhantomReference to the used ReferenceQueue, so if this is GC'ed, no Finalizable{Weak, Soft, Phantom}References can be alive, since they reference the queue. So they have to be GC'ed before the queue itself can be GC'ed - but still, do we get the guarantee that these references will be enqueued to the ReferenceQueue at the order they get "garbage collected" (as if they get GC'ed one by one)? The code implies that there is some kind of guarantee, otherwise unprocessed references could theoretically remain in the queue. Thanks

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  • Validation without ServiceLocator

    - by Dmitriy Nagirnyak
    Hi, I am getting back again and again to it thinking about the best way to perform validation on POCO objects that need access to some context (ISession in NH, IRepository for example). The only option I still can see is to use S*ervice Locator*, so my validation would look like: public User : ICanValidate { public User() {} // We need this constructor (so no context known) public virtual string Username { get; set; } public IEnumerable<ValidationError> Validate() { if (ServiceLocator.GetService<IUserRepository>().FindUserByUsername(Username) != null) yield return new ValidationError("Username", "User already exists.") } } I already use Inversion Of control and Dependency Injection and really don't like the ServiceLocator due to number of facts: Harder to maintain implicit dependencies. Harder to test the code. Potential threading issues. Explicit dependency only on the ServiceLocator. The code becomes harder to understand. Need to register the ServiceLocator interfaces during the testing. But on the other side, with plain POCO objects, I do not see any other way of performing the validation like above without ServiceLocator and only using IoC/DI. So the question would be: is there any way to use DI/IoC for the situation described above? Thanks, Dmitriy.

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  • Delete NSManageObject at the event tableView:commitEditingStyle:forRowAtIndexPath:

    - by David.Chu.ca
    I got exception when I tried to delete one NSManageObject at the event of tableView:commitEditingStyle:forRowAtIndexPath:. Here is the part of my codes: - (void)tableView:(..)tableView commitEditingStyle:(..)editingStyle forRowAtIndexPath:(..)indexPath { if (editingStyle == UITableViewCellEditingStyleDelete) { [managedObjectContext deleteObject: [fetchedResultController objectAtIndexPath:indexPath]]; ... } } The exception was thrown at the line of deleteObject:(method of my local NSManagedObjectContext). This is the exception message: uncaught exception 'NSObjectInaccessibleException', reason: 'The NSManagedObject with ID:0x3d07a30 <x-coredata://0D2CC9CB-042B-496D-B3FE-5F1ED64EAB97/paymentType/p2> has been invalidated.' I tried to get entity object first and then to delete it. The entity looks OK but still the exception was at delete: NSManagedObject *entityToDelete = [fetchedResultsController objectAtIndexPath:indexPath]; [mangedObjectContext deleteObject:entityToDelete]; // Exception again. I am not sure if the entity object retrieved from the fetchedResultsController(NSFetchedResultsController type) cannot be deleted? If so, is there any other way to get the entity object for deleting? I found that in the Apple's Core Data Tutorial for iPhone with events example, there is on NSArray to hold event entity objects. I am not sure if that's necessory to use NSArray to hold my local entity objects and then use it for deleting?

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  • Retrieve data from .dat file.

    - by Zach
    We have an application which requires us to read data from a file (.dat) dynamically using deserialization. We are actually getting first object and it throws null pointer exception when we are accessing other objects using a "for" loop. File file=null; FileOutputStream fos=null; BufferedOutputStream bos=null; ObjectOutputStream oos=null; try{ file=new File("account4.dat"); fos=new FileOutputStream(file,true); bos=new BufferedOutputStream(fos); oos=new ObjectOutputStream(bos); oos.writeObject(m); System.out.println("object serialized"); amlist=new MemberAccountList(); oos.close(); } catch(Exception ex){ ex.printStackTrace(); } Reading objects: try{ MemberAccount m1; file=new File("account4.dat");//add your code here fis=new FileInputStream(file); bis=new BufferedInputStream(fis); ois=new ObjectInputStream(bis); System.out.println(ois.readObject()); while(ois.readObject()!=null){ m1=(MemberAccount)ois.readObject(); System.out.println(m1.toString()); }/mList.addElement(m1); // Here we have the issue throwing null pointer exception Enumeration elist=mList.elements(); while(elist.hasMoreElements()){ obj=elist.nextElement(); System.out.println(obj.toString()); }/ } catch(ClassNotFoundException e){ } catch(EOFException e){ System.out.println("end"); } catch(Exception ex){ ex.printStackTrace(); }

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  • Oracle T4CPreparedStatement memory leaks?

    - by Jay
    A little background on the application that I am gonna talk about in the next few lines: XYZ is a data masking workbench eclipse RCP application: You give it a source table column, and a target table column, it would apply a trasformation (encryption/shuffling/etc) and copy the row data from source table to target table. Now, when I mask n tables at a time, n threads are launched by this app. Here is the issue: I have run into a production issue on first roll out of the above said app. Unfortunately, I don't have any logs to get to the root. However, I tried to run this app in test region and do a stress test. When I collected .hprof files and ran 'em through an analyzer (yourKit), I noticed that objects of oracle.jdbc.driver.T4CPreparedStatement was retaining heap. The analysis also tells me that one of my classes is holding a reference to this preparedstatement object and thereby, n threads have n such objects. T4CPreparedStatement seemed to have character arrays: lastBoundChars and bindChars each of size char[300000]. So, I researched a bit (google!), obtained ojdbc6.jar and tried decompiling T4CPreparedStatement. I see that T4CPreparedStatement extends OraclePreparedStatement, which dynamically manages array size of lastBoundChars and bindChars. So, my questions here are: Have you ever run into an issue like this? Do you know the significance of lastBoundChars / bindChars? I am new to profiling, so do you think I am not doing it correct? (I also ran the hprofs through MAT - and this was the main identified issue - so, I don't really think I could be wrong?) I have found something similar on the web here: http://forums.oracle.com/forums/thread.jspa?messageID=2860681 Appreciate your suggestions / advice.

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  • Removing a fields from a dynamic ModelForm

    - by Jérôme Pigeot
    In a ModelForm, i have to test user permissions to let them filling the right fields : It is defined like this: class TitleForm(ModelForm): def __init__(self, user, *args, **kwargs): super(TitleForm,self).__init__(*args, **kwargs) choices = [] # company if user.has_perm("myapp.perm_company"): self.fields['company'] = forms.ModelChoiceField(widget=forms.HiddenInput(), queryset=Company.objects.all(), required=False) choices.append('Company') # association if user.has_perm("myapp.perm_association") self.fields['association'] = forms.ModelChoiceField(widget=forms.HiddenInput(), queryset=Association.objects.all(), required=False) choices.append('Association') # choices self.fields['type_resource'] = forms.ChoiceField(choices = choices) class Meta: Model = Title This ModelForm does the work : i hide each field on the template and make them appearing thanks to javascript... The problem is this ModelForm is that each field defined in the model will be displayed on the template. I would like to remove them from the form if they are not needed: exemple : if the user has no right on the model Company, it won't be used it in the rendered form in the template. The problem of that is you have to put the list of fields in the Meta class of the form with fields or exclude attribute, but i don't know how to manage them dynamically. Any Idea?? Thanks by advance for any answer.

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  • How do you create a non-Thread-based Guice custom Scope?

    - by Russ
    It seems that all Guice's out-of-the-box Scope implementations are inherently Thread-based (or ignore Threads entirely): Scopes.SINGLETON and Scopes.NO_SCOPE ignore Threads and are the edge cases: global scope and no scope. ServletScopes.REQUEST and ServletScopes.SESSION ultimately depend on retrieving scoped objects from a ThreadLocal<Context>. The retrieved Context holds a reference to the HttpServletRequest that holds a reference to the scoped objects stored as named attributes (where name is derived from com.google.inject.Key). Class SimpleScope from the custom scope Guice wiki also provides a per-Thread implementation using a ThreadLocal<Map<Key<?>, Object>> member variable. With that preamble, my question is this: how does one go about creating a non-Thread-based Scope? It seems that something that I can use to look up a Map<Key<?>, Object> is missing, as the only things passed in to Scope.scope() are a Key<T> and a Provider<T>. Thanks in advance for your time.

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  • Asynchronous daemon processing / ORM interaction with Django

    - by perrierism
    I'm looking for a way to do asynchronous data processing with a daemon that uses Django ORM. However, the ORM isn't thread-safe; it's not thread-safe to try to retrieve / modify django objects from within threads. So I'm wondering what the correct way to achieve asynchrony is? Basically what I need to accomplish is taking a list of users in the db, querying a third party api and then making updates to user-profile rows for those users. As a daemon or background process. Doing this in series per user is easy, but it takes too long to be at all scalable. If the daemon is retrieving and updating the users through the ORM, how do I achieve processing 10-20 users at a time? I would use a standard threading / queue system for this but you can't thread interactions like models.User.objects.get(id=foo) ... Django itself is an asynchronous processing system which makes asynchronous ORM calls(?) for each request, so there should be a way to do it? I haven't found anything in the documentation so far. Cheers

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  • .NET: How do I know if I have an unmanaged resource?

    - by Shiftbit
    I've read that unmanaged resource are considered file handles, streams, anything low level. Does MSDN or any other source explain how to recognize an unmanaged resource? I can't seem to find any examples on the net that show unmanaged code, all the examples just have comments that say unmanaged code here. Can someone perhaps provide a realworld example where I would handle an unmanaged resources in an IDispose interface? I provided the IDisposable interface for your convience. How do I identify an unmanaged resource? Thanks in advance! IDisposable Reference Public Class Sample : Implements IDisposable Private disposedValue As Boolean = False 'To detect redundant calls ' IDisposable Protected Overridable Sub Dispose(ByVal disposing As Boolean) If Not Me.disposedValue Then If disposing Then ' TODO: free other state (managed objects). End If ' TODO: free your own state (unmanaged objects). ' TODO: set large fields to null. End If Me.disposedValue = True End Sub ' This code added by Visual Basic to correctly implement the disposable pattern. Public Sub Dispose() Implements IDisposable.Dispose ' Do not change this code. Put cleanup code in Dispose(ByVal disposing As Boolean) above. Dispose(True) GC.SuppressFinalize(Me) End Sub End Class

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  • How to build n-layered web architecture with PHP?

    - by Alex
    I have a description and design of a website and I need to redesign it to allow for new requirements. The website's purpose is the offering of government's contracts and bidding opportunities for different businesses.I'm dealing with the 3-tier architecture PHP website comprising of the user-interface tier(client's web browser),business logic layer(Apache web server with PHP engine in it and a couple of applications running within a web server as well) and a database layer(local mysql database). Now,i need to redesign it to su???rt distributed n-tier architecture and specify how I would go about it.After long hours of research i came to this solution: business logic should be separated into presentation and purely business logic tier to allow for n-layer architecture(user-interface,presentation tier,b.logic and data tier).I have decided to use ??? just for the presentation(since the original existing website is in PHP) and use it within apache web server.In the business logic i want to use J2?? implementation technology instead of implementing it in PHP(i.e using Zend app.server and smarty template) cz J2EE can provide much more essential container services which are essential for business logic,its robustness,maintainability and different critical business operations which will be carried out by the g?v?rnment's website.So,particularly,i want to use J??ss app.server with ?J? business objects in it which would provide all the b.logic in java and would interact with the database and so forth.In order to connect PHP on a web server with java on app.server i'm gonna use PHP/Java bridge API (or maybe Quercus or SOAP is better?).Finally,i have my data tier with mysql which will communicate with b.logic via JD??.Payment system application in ???.server is gonna use S??? to talk with credit card company. From your professional point of view,does it sound like a good way of redesigning the original website to allow for n-tier architecture considering the specifics of the website and the criticality of its operations?(payment system is included in it)or u would personally prefer to use PHP business objects for business logic as well instead of J2EE?If you have any wiser recommendation or some alternative,please let me know what is right or wrong in my current solution. H??? to hear your professional advice very s??n (I'm new to the area of web development) Thanks in advance

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  • DDD and Client/Server apps

    - by Christophe Herreman
    I was wondering if any of you had successfully implemented DDD in a Client/Server app and would like to share some experiences. We are currently working on a smart client in Flex and a backend in Java. On the server we have a service layer exposed to the client that offers CRUD operations amongst some other service methods. I understand that in DDD these services should be repositories and services should be used to handle use cases that do not fit inside a repository. Right now, we mimic these services on the client behind an interface and inject implementations (Webservices, RMI, etc) via an IoC container. So some questions arise: should the server expose repositories to the client or do we need to have some sort of a facade (that is able to handle security for instance) should the client implement repositories (and DDD in general?) knowing that in the client, most of the logic is view related and real business logic lives on the server. All communication with the server happens asynchronously and we have a single threaded programming model on the client. how about mapping client to server objects and vice versa? We tried DTO's but reverted back to exposing the state of our objects and mapping directly to them. I know this is considered bad practice, but it saves us an incredible amount of time) In general I think a new generation of applications is coming with the growth of Flex, Silverlight, JavaFX and I'm curious how DDD fits into this.

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  • No test coverage files generated for Unit Test bundle in Xcode

    - by John Gallagher
    The Problem I've got a Cocoa project on the desktop and I'm using Xcode 3.2.1 on Snow Leopard 10.6.2. I want to generate code coverage files for my Unit Test Target in Xcode. What I've Tried As articles like this one suggest, I've adjusted the build settings to: “Generate Test Coverage Files” checked “Instrument Program Flow” checked “-lgcov” added to “Other Linker Flags” I've also set the Run Script section of the test target to have the following: # Run the unit tests in this test bundle. "${SYSTEM_DEVELOPER_DIR}/Tools/RunUnitTests" # Run gcov on the framework getting tested if [ "${CONFIGURATION}" = 'Coverage' ]; then FRAMEWORK_NAME=LapsusInterpretationEngine FRAMEWORK_OBJ_DIR=${OBJROOT}/${FRAMEWORK_NAME}.build/${CONFIGURATION}/EngineTests.build/Objects-normal/${NATIVE_ARCH} mkdir -p coverage pushd coverage find ${OBJROOT} -name *.gcda -exec gcov -o ${FRAMEWORK_OBJ_DIR} {} \; popd fi Since my Framework name is LapsusInterpretationEngine but my target is named EngineTests, I put this directly into the FRAMEWORK_OBJ_DIR but this didn't seem to help. I've tried cleaning before building. I've made sure all the above build settings apply to both the Unit Test Target and the Application Target. What I Get No .gcda or .gcno files anywhere in the build directory I'm using. I point CoverStory to the Objects-normal directory in my builds folder and it complains that there's nothing there for it to read. I must be doing something really obvious wrong. Anyone any ideas? I have tried the "EngineTests.build" directory being ${FRAMEWORK_NAME} and this gives the same results.

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  • Passing viewmodel to actionresult creates new viewmodel

    - by Jonas Bohez
    I am using a viewmodel, which i then when to send to an actionresult to use (the modified viewmodel) But in the controller, i lose the list and objects in my viewmodel. This is my view: @using PigeonFancier.Models @model PigeonFancier.Models.InschrijvingModel @using (Html.BeginForm("UpdateInschrijvingen","Melker",Model)) { <div> <fieldset> <table> @foreach (var item in Model.inschrijvingLijst) { <tr> <td>@Html.DisplayFor(model => item.Duif.Naam)</td> <td> @Html.CheckBoxFor(model => item.isGeselecteerd)</td> </tr> } </table> <input type="submit" value="Wijzigen"/> </fieldset> </div> } This is my controller, which does nothing at the moment until i can get the full viewmodel back from the view. public ActionResult UpdateInschrijvingen(InschrijvingModel inschrijvingsModel) { // inschrijvingsModel is not null, but it creates a new model before it comes here with //Use the model for some updates return RedirectToAction("Inschrijven", new { vluchtId = inschrijvingsModel.vlucht.VluchtId }); } This is the model with the List and some other objects who become null because it creates a new model when it comes back from the view to the actionresult public class InschrijvingModel { public Vlucht vlucht; public Duivenmelker duivenmelker; public List<CheckBoxModel> inschrijvingLijst { get; set; } public InschrijvingModel() { // Without this i get, No parameterless constructor defined exception. // So it uses this when it comes back from the view to make a new model } public InschrijvingModel(Duivenmelker m, Vlucht vl) { inschrijvingLijst = new List<CheckBoxModel>(); vlucht = vl; duivenmelker = m; foreach (var i in m.Duiven) { inschrijvingLijst.Add(new CheckBoxModel(){Duif = i, isGeselecteerd = i.IsIngeschrevenOpVlucht(vl)}); } } What is going wrong and how should i fix this problem please? Thanks

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  • Parsing Lisp S-Expressions with known schema in C#

    - by Drew Noakes
    I'm working with a service that provides data as a Lisp-like S-Expression string. This data is arriving thick and fast, and I want to churn through it as quickly as possible, ideally directly on the byte stream (it's only single-byte characters) without any backtracking. These strings can be quite lengthy and I don't want the GC churn of allocating a string for the whole message. My current implementation uses CoCo/R with a grammar, but it has a few problems. Due to the backtracking, it assigns the whole stream to a string. It's also a bit fiddly for users of my code to change if they have to. I'd rather have a pure C# solution. CoCo/R also does not allow for the reuse of parser/scanner objects, so I have to recreate them for each message. Conceptually the data stream can be thought of as a sequence of S-Expressions: (item 1 apple)(item 2 banana)(item 3 chainsaw) Parsing this sequence would create three objects. The type of each object can be determined by the first value in the list, in the above case "item". The schema/grammar of the incoming stream is well known. Before I start coding I'd like to know if there are libraries out there that do this already. I'm sure I'm not the first person to have this problem.

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  • XNA 2D mouse picking

    - by Corndog
    I'm working on a simple 2D Real time strategy game using XNA. Right now I have reached the point where I need to be able to click on the sprite for a unit or building and be able to reference the object associated with that sprite. From the research I have done over the last three days I have found many references on how to do "Mouse picking" in 3D which does not seem to apply to my situation. I understand that another way to do this is to simply have an array of all "selectable" objects in the world and when the player clicks on a sprite it checks the mouse location against the locations of all the objects in the array. the problem I have with this approach is that it would become rather slow if the number of units and buildings grows to larger numbers. (it also does not seem very elegant) so what are some other ways I could do this. (Please note that I have also worked over the ideas of using a Hash table to associate the object with the sprite location, and using a 2 dimensional array where each location in the array represents one pixel in the world. once again they seem like rather clunky ways of doing things.)

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  • Is there added overhead to looking up a column in a DataTable by name rather than by index?

    - by Ben McCormack
    In a DataTable object, is there added overhead to looking up a column value by name thisRow("ColumnA") rather than by the column index thisRow(0)? In which scenarios might this be an issue. I work on a team that has lots of experience writing VB6 code and I noticed that didn't do column lookups by name for DataTable objects or data grids. Even in .NET code, we use a set of integer constants to reference column names in these types of objects. I asked our team lead why this was so, and he mentioned that in VB6, there was a lot of overhead in looking up data by column name rather than by index. Is this still true for .NET? Example code (in VB.NET, but same applies to C#): Public Sub TestADOData() Dim dt As New DataTable 'Set up the columns in the DataTable ' dt.Columns.Add(New DataColumn("ID", GetType(Integer))) dt.Columns.Add(New DataColumn("Name", GetType(String))) dt.Columns.Add(New DataColumn("Description", GetType(String))) 'Add some data to the data table ' dt.Rows.Add(1, "Fred", "Pitcher") dt.Rows.Add(3, "Hank", "Center Field") 'Method 1: By Column Name ' For Each r As DataRow In dt.Rows Console.WriteLine( _ "{0,-2} {1,-10} {2,-30}", r("ID"), r("Name"), r("Description")) Next Console.WriteLine() 'Method 2: By Column Name ' For Each r As DataRow In dt.Rows Console.WriteLine("{0,-2} {1,-10} {2,-30}", r(0), r(1), r(2)) Next End Sub Is there an case where method 2 provides a performance advantage over method 1?

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  • NoSuchMethodError in Java using XStream

    - by Brad Germain
    I'm trying to save a database into a file using XStream and then open it again later using XStream and deserialize it back into the objects it was in previously. The database consists of an arraylist of tables, which consists of an arraylist of a data class where the data class contains an arraylist of objects. I'm basically trying to create an sql compiler. I'm currently getting a java.lang.NoSuchMethodError because of the last line in the load method. Here's what I have: Save Method public void save(Database DB){ File file = new File(DB.getName().toUpperCase() + ".xml"); //Test sample DB.createTable("TBL1(character(a));"); DB.tables.getTable("TBL1").rows.add(new DataList()); DB.tables.getTable("TBL1").rows.getRow(0).add(10); XStream xstream = new XStream(); //Database xstream.alias("Database", Database.class); //Tables xstream.alias("Table", Table.class); //Rows xstream.alias("Row", DataList.class); //Data //xstream.alias("Data", Object.class); //String xml = xstream.toXML(DB); Writer writer = null; try { writer = new FileWriter(file); writer.write(xstream.toXML(DB)); writer.close(); } catch (IOException e) { e.printStackTrace(); } } Load Method public void Load(String dbName){ XStream xstream = new XStream(); BufferedReader br; StringBuffer buff = null; try { br = new BufferedReader(new FileReader(dbName + ".xml")); buff = new StringBuffer(); String line; while((line = br.readLine()) != null){ buff.append(line); } } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } database = (Database)xstream.fromXML(buff.toString()); }

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  • (C#) Get index of current foreach iteration

    - by Graphain
    Hi, Is there some rare language construct I haven't encountered (like the few I've learned recently, some on Stack Overflow) in C# to get a value representing the current iteration of a foreach loop? For instance, I currently do something like this depending on the circumstances: int i=0; foreach (Object o in collection) { ... i++; } Answers: @bryansh: I am setting the class of an element in a view page based on the position in the list. I guess I could add a method that gets the CSSClass for the Objects I am iterating through but that almost feels like a violation of the interface of that class. @Brad Wilson: I really like that - I've often thought about something like that when using the ternary operator but never really given it enough thought. As a bit of food for thought it would be nice if you could do something similar to somehow add (generically to all IEnumerable objects) a handle on the enumerator to increment the value that an extension method returns i.e. inject a method into the IEnumerable interface that returns an iterationindex. Of course this would be blatant hacks and witchcraft... Cool though... @crucible: Awesome I totally forgot to check the LINQ methods. Hmm appears to be a terrible library implementation though. I don't see why people are downvoting you though. You'd expect the method to either use some sort of HashTable of indices or even another SQL call, not an O(N) iteration... (@Jonathan Holland yes you are right, expecting SQL was wrong) @Joseph Daigle: The difficulty is that I assume the foreach casting/retrieval is optimised more than my own code would be. @Jonathan Holland: Ah, cheers for explaining how it works and ha at firing someone for using it.

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