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• How are value types implemented in .NET

  - by Michael

  Been looking around the net and can't find any articles about how value types are actually implemented. For instance, an Int32 is a struct and it's direct parent is System.ValueType and that's ultimate parent is System.Object. Object is a class - I imagine ValueType is a class? What's the class hierarchy? What part does the CLR have to play? At what stage and how does the CLR know to allocate value types to the stack? (FYI, I am aware that value types are stored where they are declared).

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• Connecting data to a GUI - OOP

  - by tau

  I have an application with several graphs and tables on it. I worked fast and just made classes like Graph and Table that each contained a request object (pseudo-code): class Graph { private request; public function setDateRange(dateRange) { request.setDateRange(dateRange); } public function refresh() { request.getData(function() { //refresh the display }); } } Upon a GUI event (say, someone changes the date range dropdown), I'd just call the setters on the Graph instance and then refresh it. Well, when I added other GUI elements like tables and whatnot, they all basically had similar methods (setDateRange and other things common to the request). What are some more elegant OOP ways of doing this? The application is very simple and I don't want to over-architect it, but I also don't want to have a bunch of classes with basically the same methods that are just routing to a request object. I also don't want to set up each GUI class as inheriting from the request class, but I'm open to any ideas really.

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• How to run xunit in Visual Studio 2012?

  - by user1978421

  I am very new to unit testing. I have been following the procedures for creating a unit test in visual studio 2012 on http://channel9.msdn.com/Events/TechEd/Europe/2012/DEV214. The test just won't start. And it will prompt me "A project with an Output Type of Class Library cannot be started directly. In order to debug this project, add an executable project to this solution which references the library project. Set an executable project as the startup project. Even though I attached the unit test class code to a console program, the test does not start and the test explorer is empty. In the video, it doesn't need to have any running program. The lady only created a class library, and the test will run. what should I do? Note. there is no "create unit test" on the mouse right click menu

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• What is this Hash-like/Tree-like Construct Called?

  - by viatropos

  I want to create a "Config" class that acts somewhere between a hash and a tree. It's just for storing global values, which can have a context. Here's how I use it: Config.get("root.parent.child_b") #=> "value" Here's what the class might look like: class Construct def get(path) # split path by "." # search tree for nodes end def set(key, value) # split path by "." # create tree node if necessary # set tree value end def tree { :root => { :parent => { :child_a => "value", :child_b => "another value" }, :another_parent => { :something => { :nesting => "goes on and on" } } } } end end Is there a name for this kind of thing, somewhere between Hash and Tree (not a Computer Science major)? Basically a hash-like interface to a tree.

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• Identical CSS behaves differently when applied to either body or a div

  - by Razor

  Using a DIV as container <div class="container"> <div class="half-hidden"></div> </div> CSS .container { margin: 20px auto 0; width: 200px; height: 200px; border: 1px solid red; position: relative; overflow: hidden; } .half-hidden { position: absolute; top: 10px; bottom: 10px; left: -50px; width: 100px; border: 1px solid teal; } Using body as container <div class="half-hidden"></div> CSS Replace the above .container with body Why?

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• is there some lightweight tecnique for adding type safety to identifier properties?

  - by shoren

  After using C++ I got used to the concept of Identifier which can be used with a class for the type, provides type safety and has no runtime overhead (the actual size is the size of the primitive). I want to do something like that, so I will not make mistakes like: personDao.find(book.getId());//I want compilation to fail personDao.find(book.getOwnerId());//I want compilation to succeed Possible solutuions that I don't like: For every entity have an entity id class wrapping the id primitive. I don't like the code bloat. Create a generic Identifier class. Code like this will not compile: void foo(Identifier book); void foo(Identifier person); Does anyone know of a better way? Is there a library with a utility such as this? Is implementing this an overkill? And the best of all, can this be done in Java without the object overhead like in C++?

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• GetValue on static field inside nested classes.

  - by Sir Gallahad

  Hi... I have the following class declared. I need to retreive the class structure and the static values without instanciate it. public MyClass() { public static string field = "Value"; public nestedClass() { public static string nestedField = "NestedValue"; } } I've successfuly used GetFields and GetNestedType to recover the class structure and GetValue(null) works fine on field, but not on nestedField. Let me sample: var fi = typeof(MyClass).GetField("field", BindingFlags.Public | BindingFlags.Static); var nt = typeof(MyClass).GetNestedType("nestedClass", BindingFlags.Public); var nfi = nt.GetField("nestedField", BindingFlags.Public | BindingFlags.Static); // All the above references are detected correctly var value = fi.GetValue(null); // until here everything works fine. value == "Value" var nestedValue = nfi.GetValue(null); // this one does not work!! Anyone knows why the last line does not work and how to work around? Thanks.

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• c++ inheritance

  - by Meloun

  Hi, i am trouble with this.. Is there some solution or i have to keep exactly class types? //header file Class Car { public: Car(); virtual ~Car(); }; class Bmw:Car { public: Bmw(); virtual ~Bmw(); }; void Start(Car& mycar) {}; //cpp file Car::Car(){} Car::~Car() {} Bmw::Bmw() :Car::Car(){} Bmw::~Bmw() {} int main() { Car myCar; Bmw myBmw; Start(myCar); //works Start(myBmw); //!! doesnt work return 0; }

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• How do I best write my own background-working and communicatible (sending progress updates and getti

  - by Ivan

  I have to develop a class which can run it's own hard-coded task in a background thread and communicate with container class sending him progress updates and taking messages from it. I believe I am going to extend BackgroundWorker class but it looks a bit weird to extend and I haven't managed to find a good example wit Google. Can you share a link to a good example of solving such a task? Please don't offer placing a BackgroundWorker visually on a form and reading the standard tutorial, it's not for my case. Maybe I'd better not extend but encapsulate a BackgroundWorker, but I hardly understand how to use it outide WinForms designer either :-(

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• Which Java library lets me initialize an object's properties from a properties file?

  - by Kjetil Ødegaard

  Is there a Java library that lets you "deserialize" a properties file directly into an object instance? Example: say you have a file called init.properties: username=fisk password=frosk and a Java class with some properties: class Connection { private String username; private String password; public void setUsername(String username) { this.username = username; } public void setPassword(String password) { this.password = password; } } I want to do this: Connection c = MagicConfigurator.configure("init.properties", new Connection()) and have MagicConfigurator apply all the values from the properties file to the Connection instance. Is there a library with a class like this?

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• Problem mapping data located in a NSMutableArray

  - by Graeme

  I have an NSMutableArray which contains some addresses which I need to map using Apple's MapKit SDK which I can't seem to get to load. The NSLog keeps telling me that the data source is (null) and a 0x0 error displays when I attempt to print out the array. Any ideas? The data is parsed and stored from another class, perhaps I'm not linking it across properly? The data is originally gathered from an RSS feed, bought into the app with an IMporter class, and then displayed in a table view. I want to be able to connect into that data with my mapping class, but am struggling to do so.

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• Hibernate - One design problem

  - by Yatendra Goel

  I am learning Hibernate from the tutorial on JBoss website. I have a confusion in a code example located here. There is a Cat class code at 4.1. A simple POJO example. This Cat class has a reference to his mother as private Cat mother; Q1. If the class has an identifier property as id, then wouldn't it be better to store the cat's mother's id instead of cat's mother object. means instead of private Cat mother; wouldn't it be better to have private long motherId; `

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• MVVM Binding To Property == Null

  - by LnDCobra

  I want to show some elements when a property is not null. What is the best way of achieving this? The following is my ViewModel: class ViewModel : ViewModelBase { public Trade Trade { get { return _trade; } set { SetField(ref _trade, value, () => Trade); } } private Trade _trade; } ViewModelBase inherits INotifyPropertyChanged and contains SetField() The Following is the Trade class: public class Trade : INotifyPropertyChaged { public virtual Company Company { get { return _company; } set { SetField(ref _company, value, () => Company); } } private Company _company; ...... } This is part of my View.xaml <GroupBox Visibility="{Binding Path=Trade.Company, Converter={StaticResource boolToVisConverter}}" /> I would like this groupbox to show only if Trade.Company is not null (so when a user selects a company). Would I need to create a custom converter to check for null and return the correct visibility or is there one in .NET?

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• Is this a valid, lazy, thread-safe Singleton implementation for C#?

  - by Matthew

  I implemented a Singleton pattern like this: public sealed class MyClass { ... public static MyClass Instance { get { return SingletonHolder.instance; } } ... static class SingletonHolder { public static MyClass instance = new MyClass (); } } From Googling around for C# Singleton implementations, it doesn't seem like this is a common way to do things in C#. I found one similar implementation, but the SingletonHolder class wasn't static, and included an explicit (empty) static constructor. Is this a valid, lazy, thread-safe way to implement the Singleton pattern? Or is there something I'm missing?

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• Should we avoid to use Object as the input parameter/ output value of a method?

  - by developer.cyrus

  Take Java syntax as an example, though the question itself is language independent. If the following snippet takes an object MyAbstractEmailTemplate as input argument in the method setTemplate, the class MyGateway will then become tightly-coupled with the object MyAbstractEmailTemplate, which lessens the re-usability of the class MyGateway. A compromise is to use dependency-injection to ease the instantiation of MyAbstractEmailTemplate. This might solve the coupling problem to some extent, but the interface is still rigid, hardly providing enough ?exibility to other developers/ applications. So if we only use primitive data type (or even plain XML in web service) as the input/ output of a method, it seems the coupling problem no longer exists. So what do you think? public class MyGateway { protected MyAbstractEmailTemplate template; publoc void setTemplate(MyAbstractEmailTemplate template) { this.template = template; } }

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• WPF textblock binding question.

  - by the empirical programmer

  I'm trying to get my head around the whole MVVM thing and binding. I have a ViewModel class which has a property that is another class. I want to bind to a (string) property of that class to the text of a textblock. I set the ViewModel as my data context for my window\page. And then do this: <TextBlock Text="{Binding ElementName=myAddressClass, Path=StreetName}" /> But this does not work. The text is empty. I can expose the StreetName directly as below and this works: <TextBlock Text="{Binding Path=StreetName}" /> So am I doing something wrong in the first example. It seems simple enough ... am I just confuse about what an elementname is or should be set to? thanks

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• Javascript Replace Child/Loop issue

  - by Charles John Thompson III

  I have this really bizarre issue where I have a forloop that is supposed to replace all divs with the class of "original" to text inputs with a class of "new". When I run the loop, it only replaces every-other div with an input, but if I run the loop to just replace the class of the div and not change the tag to input, it does every single div, and doesn't only do every-other. Here is my loop code, and a link to the live version: live version here function divChange() { var divs = document.getElementsByTagName("div"); for (var i=0; i<divs.length; i++) { if (divs[i].className == 'original') { var textInput = document.createElement('input'); textInput.className = 'new'; textInput.type = 'text'; textInput.value = divs[i].innerHTML; var parent = divs[i].parentNode; parent.replaceChild(textInput, divs[i]); } } }

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• Unable to export runnable jar, launch configuration grayed out

  - by user13107

  I am not able to figure out how to export a runnable jar in eclipse. I have a java project (project A) (written by someone else) which when imported in Eclipse, I can click Build Project and it will create a projectName.jar file under bin/ directory. That jar file contains binary *.class files. This jar file is added as external library for another java project (project B) which I want to debug. But because all the class files are binary I'm not able to do line-by-line debugging. I tried exporting Runnable Jar in Eclipse, for that I have to select a Launch Configuration. But there is no main class in project A. (I recursively grepped for main and didn't find any). What can I do to export jar of project A that contains respective source code also (which will be used in line-by-line debugging)?

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• save object associate to another object automatically

  - by Luca Romagnoli

  Hi i have these classes: class Core < ActiveRecord::Base belongs_to :resource, :polymorphic => true belongs_to :image, :class_name => 'Multimedia', :foreign_key => 'image_id' end class Place < ActiveRecord::Base has_one :core, :as => :resource end If i try do launch this: a = Place.find(5) a.name ="a" a.core.image_id = 24 a.save name is saved. image_id no i want save automatically all changes in records in relationship with place class at a.save command. is possible? thanks

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• C++ String pointers

  - by gnm

  In my previous app I had an object like this: class myType { public: int a; string b; } It had a lot of instances scattered everywhere and passed around to nearly every function. The app was slow. Profiling said that 95% of time is eaten by the string allocator function. I know how to work with the object above, but not how to work with string pointers. class myType { public: int a; string* b; } They told me to use pointers as above. How much faster is it with a string pointer? What is copied when I copy the object? How to the following using the class with the pointer: Access the string value Modify the string value without modifying the one in the object (copy?) General things that change if I use string pointers?

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• Passing an array argument from C# to a C++/CLI method

  - by jco

  I know only very little about C++/CLI, but I have a simple problem that needs a solution. I have a C++/CLI class method that takes a byte-array as a parameter. The array is of a pre-determined length, and can be allocated in C# beforehand. The array is supposed to be filled with data by the C++/CLI method. How do I declare the method and then call it from C#? I tried something like having the following in my C++/CLI class: public ref class C { public: void FillBytes(array<BYTE^>^ bytes); }; And then, in C#: o = new C(); var bytes = new byte[3]; o.FillBytes(bytes); But that didn't work at all :).

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• difference in using virtual and not using virtual

  - by numerical25

  In C++, whether you choose to use virtual or not, you can still override the base class function. The following compiles just fine... class Enemy { public: void SelectAnimation(); void RunAI(); void Interact() { cout<<"Hi I am a regular Enemy"; } private: int m_iHitPoints; }; class Boss : public Enemy { public: void Interact() { cout<<"Hi I am a evil Boss"; } }; So my question is what is the difference in using or not using the virtual function. And what is the disadvantage.

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• Generating PDF results in single page only?

  - by A T

  Generating a PDF from an email (Zurb Ink templated); but am always presented with a single page PDF. Runnable test-case: from weasyprint import HTML, CSS from urllib2 import urlopen if __name__ == '__main__': html = urlopen('http://zurb.com/ink/downloads/templates/basic.html').read() html = html.replace('<p class=\"lead\">', '{0}<p class=\"lead\">'.format( '<p class=\"lead\">{0}</p>'.format("foobar " * 50) * 50)) HTML(string=html).write_pdf('foo.pdf', stylesheets=[ CSS(string='@page { size: A4; margin: 2cm };' '* { float: none !important; };' '@media print { nav { display: none; } }') ]) How do I get a multi-page PDF?

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• How can I update only certain fields in a Django model form?

  - by J. Frankenstein

  I have a model form that I use to update a model. class Turtle(models.Model): name = models.CharField(max_length=50, blank=False) description = models.TextField(blank=True) class TurtleForm(forms.ModelForm): class Meta: model = Turtle Sometimes I don't need to update the entire model, but only want to update one of the fields. So when I POST the form only has information for the description. When I do that the model never saves because it thinks that the name is being blanked out while my intent is that the name not change and just be used from the model. turtle_form = TurtleForm(request.POST, instance=object) if turtle_form.is_valid(): turtle_form.save() Is there any way to make this happen? Thanks!

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• Django Forms: TimeField Validation

  - by Tom

  I feel like I'm missing something obvious here. I have a Django form with a TimeField on it. I want to be able to allow times like "10:30AM", but I cannot get it to accept that input format or to use the "%P" format (which has a note attached saying it's a "Proprietary extension", but doesn't say where it comes from). Here's the gist of my form code: calendar_widget = forms.widgets.DateInput(attrs={'class': 'date-pick'}, format='%m/%d/%Y') time_widget = forms.widgets.TimeInput(attrs={'class': 'time-pick'}) valid_time_formats = ['%P', '%H:%M%A', '%H:%M %A', '%H:%M%a', '%H:%M %a'] class EventForm(forms.ModelForm): start_date = forms.DateField(widget=calendar_widget) start_time = forms.TimeField(required=False, widget=time_widget, help_text='ex: 10:30AM', input_formats=valid_time_formats) end_date = forms.DateField(required=False, widget=calendar_widget) end_time = forms.TimeField(required=False, widget=time_widget, help_text='ex: 10:30AM', input_formats=valid_time_formats) description = forms.CharField(widget=forms.Textarea) Any time I submit "10:30AM", I get a validation error. The underlying model has two fields, event_start and event_end, no time fields, so I don't think the problem is in there. What stupid thing am I missing?

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