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• Confusion about Nullable<T> constraints

  - by n535

  Greetings everybody. I am sorry, if this was already asked before (searched in vain) or is really very simple, but i just can't get it. The MSDN definition of a Nullable type, states, that it is defined in a following manner: [SerializableAttribute] public struct Nullable<T> where T : struct, new() So the question is quite straightforward: How is this definition possible? Or this is just a typo? Every value type already has a default constructor. Indeed, when i try to compile something like this, the compiler reasonably says, that it is illegal to apply both constraints at the same time, because the second one is implicitly included in a first one. Thanks in advance.

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• Validations for a has_many/belongs_to relationship

  - by Craig Walker

  I have a Recipe model which has_many Ingredients (which in turn belongs_to Recipe). I want Ingredient to be existent dependent on Recipe; an Ingredient should never exist without a Recipe. I'm trying to enforce the presence of a valid Recipe ID in the Ingredient. I've been doing this with a validates :recipe, :presence => true (Rails 3) statement in Ingredient. This works fine if I save the Recipe before adding an Ingredient to it's ingredients collection. However, if I don't have explicit control over the saving (such as when I'm creating a Recipe and its Ingredients from a nested form) then I get an error: Ingredients recipe can't be blank I can get around this simply by dropping the presence validation on Ingredient.recipe. However, I don't particularly like this, as it means I'm working without a safety net. What is the best way to enforce existence-dependence in Rails? Things I'm considering (please comment on the wisdom of each): Adding a not-null constraint on the ingredients.recipe_id database column, and letting the database do the checking for me. A custom validation that somehow checks whether the Ingredient is in an unsaved recipe's ingredient collection (and thus can't have a recipe_id but is still considered valid).

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• How to set default values to the properties of dynamically loaded types at runtime for XML serializa

  - by Erkan Y.

  I need to serialize dynamically loaded types' classes using XMLSerializer. When using XML serializer non initialized values are not being serialized. I dont have control over the assemblies I am working with so can not use XML attributes for specifying default values on properties. So I think I need to set all properties and sub properties to their default values recursively and then serialize. ( Please let me know if there is any better way ) Followed this : Activator.CreateInstance(propType); but above line complains about not having a parameterless constructor for some types. Tried this : subObject = FormatterServices.GetUninitializedObject(propType); but this one gives an error "value was invalid" with no inner exception. Please let me know if you need any further information.

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• How can I add a field with an array value to my Perl object?

  - by superstar

  What's the difference between these two constructors in perl? 1) sub new { my $class = shift; my $self = {}; $self->{firstName} = undef; $self->{lastName} = undef; $self->{PEERS} = []; bless ($self, $class); return $self; } 2) sub new { my $class = shift; my $self = { _firstName => shift, _lastName => shift, _ssn => shift, }; bless $self, $class; return $self; } I am using the second one so far, but I need to implement the PEERS array in the second one? How do I do it with the second constructor and how can we use get and set methods on those array variables?

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• different explanation

  - by Delirium tremens

  The following code echoes 5, not 10: $global_obj = null; class my_class { var $value; function my_class() { global $global_obj; $global_obj = &$this; } } $a = new my_class; $a->my_value = 5; $global_obj->my_value = 10; echo $a->my_value; "Upon first examination, it would seem that the constructor of my_class stores a reference to itself inside the $global_obj variable. Therefore, one would expect that, when we later change the value of $global_obj-my_value to 10, the corresponding value in $a would change as well. Unfortunately, the new operator does not return a reference, but a copy of the newly created object." Please, give me a different explanation.

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• Can't get Angular Dart Router to work

  - by JesterXL

  I've tried this syntax in AngularDart 0.11.0: Angular Dart passing data from route service into a controller module.value(RouteInitializerFn, configureRoutes); void configureRoutes(Router router, RouteViewFactory views) { print("configureRoutes"); views.configure({ 'login': ngRoute( path: '/login', view: 'login/login.tpl.html'), 'today': ngRoute( path: '/today', view: '/today/today.tpl.html') }); However, my routing function never seems to get called. I've used both a print statement and breakpoint to no avail. When I attempt to call it like so: WorkoutLoggerApplication(this.rootScope, this.router) { print("WorkoutLoggerApplication::constructor"); new Future.delayed(new Duration(seconds: 2), () { router.go("login", {}); }); } I get: Bad state: Invalid route name: login I've tried 0.10.0, but no dice. I've also tried 3 varieties of the new bind function format, both also don't seem to ever fire the routing function.

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• Error : Implementation for method missing (Delphi Prism)

  - by Ilya

  I wrote my method: LangChange type MainForm = partial class(System.Windows.Forms.Form) private ... method LangChange(); protected method Dispose(disposing: Boolean); override; public constructor; end; implementation ... method LangChange(); begin ... end; However,I have an error Error 1 (PE33) Implementation for method "Compiler.MainForm.LangChange" missing What is wrong?Help please!

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• Can anyone recommend a .Net XML Serialization library?

  - by James

  Can anyone recommend a .Net XML Serialization library (ideally open source). I am looking for a robust XML serialization library that I can throw any object at, which will produce a human readable XML representation of the public properties for logging purposes. I never need to be able to deserialize. XmlSerializer's requirement of an object having a parameter constructor is too restrictive for what I want. DataContractSerializer does not give enough control over the output (which is not particularly human-readable). Any recommendations appreciated! Thanks

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• Reading a C/C++ data structure in C# from a byte array

  - by Chris Miller

  What would be the best way to fill a C# struct from a byte[] array where the data was from a C/C++ struct? The C struct would look something like this (my C is very rusty): typedef OldStuff { CHAR Name[8]; UInt32 User; CHAR Location[8]; UInt32 TimeStamp; UInt32 Sequence; CHAR Tracking[16]; CHAR Filler[12];} And would fill something like this: [StructLayout(LayoutKind.Explicit, Size = 56, Pack = 1)]public struct NewStuff{ [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 8)] [FieldOffset(0)] public string Name; [MarshalAs(UnmanagedType.U4)] [FieldOffset(8)] public uint User; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 8)] [FieldOffset(12)] public string Location; [MarshalAs(UnmanagedType.U4)] [FieldOffset(20)] public uint TimeStamp; [MarshalAs(UnmanagedType.U4)] [FieldOffset(24)] public uint Sequence; [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 16)] [FieldOffset(28)] public string Tracking;} What is best way to copy OldStuff to NewStuff, if OldStuff was passed as byte[] array? I'm currently doing something like the following, but it feels kind of clunky. GCHandle handle;NewStuff MyStuff;int BufferSize = Marshal.SizeOf(typeof(NewStuff));byte[] buff = new byte[BufferSize];Array.Copy(SomeByteArray, 0, buff, 0, BufferSize);handle = GCHandle.Alloc(buff, GCHandleType.Pinned);MyStuff = (NewStuff)Marshal.PtrToStructure(handle.AddrOfPinnedObject(), typeof(NewStuff));handle.Free(); Is there better way to accomplish this?

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• Are we using IoC effectively?

  - by Juliet

  So my company uses Castle Windsor IoC container, but in a way that feels "off": All the data types are registered in code, not the config file. All data types are hard-coded to use one interface implementation. In fact, for nearly all given interfaces, there is and will only ever be one implementation. All registered data types have a default constructor, so Windsor doesn't instantiate an object graph for any registered types. The people who designed the system insist the IoC container makes the system better. We have 1200+ public classes, so its a big system, the kind where you'd expect to find a framework like Windsor. But I'm still skeptical. Is my company using IoC effectively? Is there an advantage to new'ing objects with Windsor than new'ing objects with the new keyword?

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• Is this a good way to identify the type of a javascript object?

  - by FK82

  Apparently neither instanceof nor typeof deliver in terms of correctly identifying the type of every javascript object. I have come up with this function and I'm looking for some feedback: function getType() { var input = arguments[0] ; var types = ["String","Array","Object","Function","HTML"] ; //!! of the top of my head for(var n=0; n < types.length; n++) { if( input.constructor.toString().indexOf( types[n] ) != -1) { document.write( types[n] ) ; } } } Thanks for reading!

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• Best way to test if a generic type is a string? (c#)

  - by Rex M

  I have a generic class that should allow any type, primitive or otherwise. The only problem with this is using default(T). When you call default on a value type or a string, it initializes it to a reasonable value (such as empty string). When you call default(T) on an object, it returns null. For various reasons we need to ensure that if it is not a primitive type, then we will have a default instance of the type, not null. Here is attempt 1: T createDefault() { if(typeof(T).IsValueType) { return default(T); } else { return Activator.CreateInstance<T>(); } } Problem - string is not a value type, but it does not have a parameterless constructor. So, the current solution is: T createDefault() { if(typeof(T).IsValueType || typeof(T).FullName == "System.String") { return default(T); } else { return Activator.CreateInstance<T>(); } } But this feels like a kludge. Is there a nicer way to handle the string case?

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• Keep a Google Maps v3 Map Hidden, show when needed

  - by Dr1Ku

  Is there a way of preventing Google Maps (JS, v3) of being displayed from the get-go ? I do some pre-processing and would like to show my 'Loading' spinner until everything is good to go (more eloquently put, hide the map -- e.g. the container div -- until all preprocessing is complete -- at which point, show the map). Hooking to the map's 'idle' event doesn't help that much, since the map is already displayed when this event hits. I know that the container div gets inline-styled by GMaps after loading, my first idea is to clear out the style attr (whilst listening to 'idle'), but it would be interesting to see if there is a way of creating the map and not displaying it until all pre-processing is done. Maybe by using an argument to the new google.maps.Map constructor, or a MapOption ? Any thoughts on this ? Thank you in advance !

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• How can I access and modify objects inside frames with AS3 in a permanent way?

  - by curro

  I have a MovieClip symbol created with flash in a fla file library. There is a textfield in frame one of this movieclip's timeline . There is another frame in the movieclip timeline. There is a custon class definition for this symbol. It is a flipping card in a memory game. I access the textfield by going to frame 2 (gotoAndStop(2)) and setting the textfield's text property ( this.field.text = "hello" ). However if I go to frame 1 and then return to frame 2, the text becomes the original one in the library's symbol. I have to modify the text propery again in a showFace method I've written. Besides, I cannot pass parameters in the constructor because it is a symbol in the library and that would give errors. I find this behaviour of flash extremely weird. Is there a way I can set properties inside frames permanently? Thank you

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• Relvance of 'public' contructor in abstract class.

  - by Amby

  Is there any relevance of a 'public' constructor in an abstract class? I can not think of any possible way to use it, in that case shouldn't it be treated as error by compiler (C#, not sure if other languages allow that). Sample Code: internal abstract class Vehicle { public Vehicle() { } } The C# compiler allows this code to compile, while there is no way i can call this contructor from the outside world. It can be called from derived classes only. So shouldn't it allow 'protected' and 'private' modifiers only. Please comment.

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• Not loading associations without proxies in NHibernate

  - by Alice

  I don't like the idea of proxy and lazy loading. I don't need that. I want pure POCO. And I want to control loading associations explicitly when I need. Here is entity public class Post { public long Id { get; set; } public long OwnerId { get; set; } public string Content { get; set; } public User Owner { get; set; } } and mapping <class name="Post"> <id name="Id" /> <property name="OwnerId" /> <property name="Content" /> <many-to-one name="Owner" column="OwnerId" /> </class> However if I specify lazy="false" in the mapping, Owner is always eagerly fetched. I can't remove many-to-one mapping because that also disables explicit loading or a query like from x in session.Query<Comment>() where x.Owner.Title == "hello" select x; I specified lazy="true" and set use_proxy_validator property to false. But that also eager loads Owner. Is there any way to load only Post entity?

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• 2 Classes need each other declared C++

  - by Prodigga

  I have a "Game" class which holds all the games settings and manages the game. I have a "Grid" class which is the grid the game is played on. The "Game" class initializes a "Grid" object as one of its members (passing itself ("this") as one of the parameters for "Grid"s constructor).. The "Grid" object therefor needs to deal with a "Game*" pointer. To do this it needs to know what "Game" is; i need to declare it before "Grid". But "Game" uses "Grid"...so it also needs "Grid" declared before it. so confused on how to include headers/etc correctly here..

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• C# property in a form class only accessable after formload event

  - by Spooky2010

  using vs2008, c# Howdy, Im instantiating and calling Form B from Form A. FormB has some custom properties, to allow me to pass it things like sqlAdaptors and dataset instances. When i instantiate and show Form B from Form A as a dialog form with a Using statement, it all works fine, but i find the properties i pass are not available in Form B until after the form_load event has fired. I was under the impression the properties when passed to a instantiated class should be available from a constructor, but this is not the case. If it try to access the properties before the form load event i get a null reference exception. Is this correct behavior ? It is very annoying. thanks for any help

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• C# how to dynamically cast an object?

  - by JL

  I am building a helper object that has a property called Mailer. In reality Mailer can be either a System.Net.Mail.MailMessage or a Mono.System.Net.Mail.MailMessage. So I would preferably only want 1 declaration of mailer. For example I don't want: private Mono.Mailing.MailMessage MonoMessage = new Mono.Mailing.MailMessage(); private System.Net.Mail.MailMessage MailMessage = new System.Net.Mail.MailMessage(); I would prefer object mailer; Then in constructor switch (software) { case EnunInternalMailingSoftware.dotnet: this.mailer = new System.Net.Mail.MailMessage(); break; case EnunInternalMailingSoftware.mono: this.mailer = new Mono.Mailing.MailMessage(); break; } The problem is that mailer has no properties at design time. So I can't compile my code. How can this be fixed, am I taking the right approach. Thanks in advance

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• Setting Nullable Integer to String Containing Nothing yields 0

  - by Brian MacKay

  I've been pulling my hair out over some unexpected behavior from nullable integers. If I set an Integer to Nothing, it becomes Nothing as expected. If I set an Integer? to a String that is Nothing, it becomes 0! Of course I get this whether I explicitly cast the String to Integer? or not. I realize I could work around this pretty easily but I want to know what I'm missing. Dim NullString As String = Nothing Dim NullableInt As Integer? = CType(NullString, Integer?) 'Expected NullableInt to be Nothing, but it's 0! NullableInt = Nothing 'This works -- NullableInt now contains Nothing. How is this EDIT: Previously I had my code up here so without the explicit conversion to 'Integer?' and everyone seemed to be fixated on that. I want to be clear that this is not an issue that would have been caught by Option Strict On -- check out the accepted answer. This is a quirk of the string-to-integer conversion rules which predate nullable types, but still impact them.

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• Accessing a Clip Inside Another Clip in a Loaded SWF-File

  - by Anders

  I'm writing a card game in AS3. The artist I'm working with has produced (in Flash CS4) a single swf-file containing all the card graphics and animations. The structure of the fla working file looks something like this: - Scene - CardGraphics (Movie Clip) - CardFront - CardBack - CardValueImage (Movie Clip) ... In the program I create 52 instances of my Card class, each having a MovieClip instance created from the loaded swf. The idea is to set the frame of the CardValueImage MovieClip to correspond to the Card instance's suit and rank member variables. However, I can't figure out how I access CardValueImage and call gotoAndStop (or whatever method I will need to call). This is basically what I want to do: // Card Class [Embed(source = 'CardGraphics.swf')] private static var CardsClip:Class; private var clip:MovieClip = new CardsClip; // Card Constructor this.valueImageFrame = suit * 13 + rank; // Calculate which frame contains the // graphical representation of this card this.clip.CardValueImage.gotoAndStop(valueImageFrame);

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• Explanation of output

  - by Anon

  My program class Building { Building() { System.out.print("b "); } Building(String name) { this(); System.out.print("bn " + name); } }; public class House extends Building { House() { System.out.print("h "); // this is line# 1 } House(String name) { this(); // This is line#2 System.out.print("hn " + name); } public static void main(String[] args) { new House("x "); } } We know that compiler will write a call to super() as the first line in the child class's constructor. Therefore should not the output be: b (call from compiler written call to super(), before line#2 b (again from compiler written call to super(),before line#1 ) h hn x But the output is b h hn x Why is that?

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• Castle Windsor: Reuse resolved component in OnCreate, UsingFactoryMethod or DynamicParameters

  - by shovavnik

  I'm trying to execute an action on a resolved component before it is returned as a dependency to the application. For example, with this graph: public class Foo : IFoo { } public class Bar { IFoo _foo; IBaz _baz; public Bar(IFoo foo, IBaz baz) { _foo = foo; _baz = baz; } } When I create an instance of IFoo, I want the container to instantiate Bar and pass the already-resolved IFoo to it, along with any other dependencies it requires. So when I call: var foo = container.Resolve<IFoo>(); The container should automatically call: container.Resolve<Bar>(); // should pass foo and instantiate IBaz I've tried using OnCreate, DynamicParameters and UsingFactoryMethod, but the problem they all share is that they don't hold an explicit reference to the component: DynamicParameters is called before IFoo is instantiated. OnCreate is called after, but the delegate doesn't pass the instance. UsingFactoryMethod doesn't help because I need to register these components with TService and TComponent. Ideally, I'd like a registration to look something like this: container.Register<IFoo, Foo>((kernel, foo) => kernel.Resolve<Bar>(new { foo })); Note that IFoo and Bar are registered with the transient life style, which means that the already-resolved instance has to be passed to Bar - it can't be "re-resolved". Is this possible? Am I missing something?

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• Resizing an image with alpha channel

  - by Hafthor

  I am writing some code to generate images - essentially I have a source image that is large and includes transparent regions. I use GDI+ to open that image and add additional objects. What I want to do next is to save this new image much smaller, so I used the Bitmap constructor that takes a source Image object and a height and width, then saved that. I was expecting the alpha channel to be smoothed like the color channels, but this did not happen -- it did result in a couple of semitransparent pixels, but overall it is very blocky. What gives? Using img As New Bitmap("source100x100.png") ''// Drawing stuff Using simg As New Bitmap(img, 20, 20) simg.Save("target20x20.png") End Using End Using Edit: I think what I want is SuperSampling, like what Paint.NET does when set to "Best Quality"

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• Trouble dragging and dropping gui components onto other .net forms using NHibernate

  - by IsaacB

  Hi, using VS2008, here. I have a GUI component that loads some stuff from a database mapped by nhibernate in its constructor. When I drag and drop this component onto another form from the toolbox, NHibernate complains that it can't find the config file in program files\visual studio 9\common7\ide. Why is it looking here for the cfg file? I'm actually calling database stuff through another project in the same solution, and the cfg file is located at the root of that project. copy/pasting the cfg file over to there does work, but I'm working with svn here and I don't want to have configuration files outside the repository. Something else that would help would be turning off how it tries to load the data in the form design screen. How would I do that?

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