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  • Declaring an enum within a class

    - by bporter
    In the following code snippet, the Color enum is declared within the Car class in order to limit the scope of the enum and to try not to "pollute" the global namespace. class Car { public: enum Color { RED, BLUE, WHITE }; void SetColor( Car::Color color ) { _color = color; } Car::Color GetColor() const { return _color; } private: Car::Color _color; }; (1) Is this a good way to limit the scope of the Color enum? Or, should I declare it outside of the Car class, but possibly within its own namespace or struct? I just came across this article today, which advocates the latter and discusses some nice points about enums: http://gamesfromwithin.com/stupid-c-tricks-2-better-enums. (2) In this example, when working within the class, is it best to code the enum as Car::Color, or would just Color suffice? (I assume the former is better, just in case there is another Color enum declared in the global namespace. That way, at least, we are explicit about the enum to we are referring.) Thanks in advance for any input on this.

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  • C++ Declaring an enum within a class

    - by bporter
    In the following code snippet, the Color enum is declared within the Car class in order to limit the scope of the enum and to try not to "pollute" the global namespace. class Car { public: enum Color { RED, BLUE, WHITE }; void SetColor( Car::Color color ) { _color = color; } Car::Color GetColor() const { return _color; } private: Car::Color _color; }; (1) Is this a good way to limit the scope of the Color enum? Or, should I declare it outside of the Car class, but possibly within its own namespace or struct? I just came across this article today, which advocates the latter and discusses some nice points about enums: http://gamesfromwithin.com/stupid-c-tricks-2-better-enums. (2) In this example, when working within the class, is it best to code the enum as Car::Color, or would just Color suffice? (I assume the former is better, just in case there is another Color enum declared in the global namespace. That way, at least, we are explicit about the enum to we are referring.) Thanks in advance for any input on this.

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  • Implementing a Version check between an Abstract class and it's implementation

    - by Michael Stum
    I have this abstract class and concrete implementation (they are in different assemblies): public abstract class MyAbstractClass { private static readonly int MyAbstractClassVersion = 1; public abstract int ImplementedVersion { get; } protected MyAbstractClass() { CheckVersion(); } private void CheckVersion() { var message = string.Format( "MyAbstractClass implements Version {0}, concrete is Version {1}", RepositoryVersion, ImplementedVersion); if (!MyAbstractClassVersion.Equals(ImplementedVersion)) throw new InvalidOperationException(message); } } public class ConcreteClass : MyAbstractClass { public ConcreteClass() : base() { // ConcreteClass is guaranteed to have // a constructor that calls the base constructor // I just simplified the example } public override int ImplementedVersion { get { return 2; } } } As you see, I call CheckVersion() from the abstract constructor, to get rid of the "virtual member call in base constructor" message, but I am not sure if that's really the way to do it. Sure, it works, but that doesn't mean it will always work, will it? Also, I wonder if I can get the name of the Concrete Type from the CheckVersion() function? I know that adding new abstract members will force an error anyway (System.TypeLoadException) and I'm not sure if I want this type of strict Versioning, but I'm just curious how it would be done properly given only the abstract class and an implementation (I know I could do it by using interfaces and/or a Factory pattern).

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  • RPG Game loop and class structure (cocos2D for iPhone)

    - by mac_55
    I'm looking to make an RPG with Cocos2D on the iPhone. I've done a fair bit of research, and I really like the model Cocos2D uses for scenes. I can instantiate a scene, set up my characters etc. and it all works really nicely... what I have problems with is structuring a game loop and separating the code from the scenes. For example, where do I put my code that will maintain the state of the game across multiple scenes? and do I put the code for events that get fired in a scene in that scene's class? or do I have some other class that separates the init code from the logic? Also, I've read a lot of tutorials that mention changing scenes, but I've read none that talk about updating a scene - taking input from the user and updating the display based on that. Does that happen in the scene object, or in a separate display engine type class. Thanks in advance!

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  • UIComponent extended class isn't showing UIComponent extended class

    - by Arno
    I have 1 class (that is extending a UIcomponent) that is representing a component. In that component I create different instances of another class that is also a UIComponent but this class doesn't show up in de first class. I see that it is running and that it has the correct hights but I got the feeling that it doesn't show up with this hights. If I trace I see the width and height is 200 X 200 but there is still nothing visible in my component I bet there is a simple solution for this problem?

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  • Java: exception-throwing class?

    - by HH
    I have classes DirReader and Search. The search uses DirReader. I want the search to know when DirReader throws exception. So how can I have class throwing exception? Currently, I use initCorrect -dummy var. Exception-style method may be more appropriate. Simplified Example Error $ javac ExceptionStatic.java ExceptionStatic.java:4: '{' expected public class ExceptionStatic throws Exception{ ^ 1 error Code import java.util.*; import java.io.*; // THIS PART NEEDS TO BE FIXED: public class ExceptionStatic throws Exception{ private static boolean initCorrect = false; public static String hello; static{ try{ hello = "hallo"; //some other conditionals in real code if( true) throw new Exception(); initCorrect=true; }catch(Exception e){ e.printStackTrace(); } } public static void main(String[] args){ if(initCorrect) System.out.println(hello); } }

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  • reference from xaml to public class in .cs class file

    - by netmajor
    I have in my WPF project file RssInfo.cs in which I have public class public class DoubleRangeRule : ValidationRule { public double Min { get; set; } public double Max { get; set; } public override System.Windows.Controls.ValidationResult Validate(object value, CultureInfo cultureInfo) { ... } } and from my XAML code in WPF window class I neet to get to this DoubleRangeRule class.. //reference to my project, all my files are in the WpfCzytanieRSS namespace xmlns:valRule="clr-namespace:WpfCzytanieRSS;assembly=WpfCzytanieRSS" <TextBox Validation.ErrorTemplate="{StaticResource TextBoxErrorTemplate}" Name="tbTitle"> <TextBox.Text> <Binding Path="Nazwa" UpdateSourceTrigger="PropertyChanged"> <Binding.ValidationRules> <valRule:DoubleRangeRule Min="0.5" Max="10"/> //error place </Binding.ValidationRules> </Binding> </TextBox.Text> </TextBox> And i get two errors: Error 1 The tag 'DoubleRangeRule' does not exist in XML namespace 'clr-namespace:WpfCzytanieRSS;assembly=WpfCzytanieRSS'. Error 2 The type 'valRule:DoubleRangeRule' was not found. Verify that you are not missing an assembly reference and that all referenced assemblies have been built. Please help to get to class DoubleRangeRule ! :)

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  • OSX Weak Linking - check if a class exists and use that class

    - by psychotik
    I'm trying to create a universal iPhone app, but it uses a class defined only in a newer version of the SDK. The framework exists on older systems, but a class defined in the framework doesn't. I know I want to use some kind of weak linking, but any documentation I can find talks about runtime checks for function existence - how do I check that a class exists?

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  • Optimizing Class Structure

    - by Derek Hammer
    I have the following class structure (abbreviated for sake of time, names changed) in my application. When I was writing the code I felt that the similarities between Action1 and Action2 should warrant some sort of generalization. I've provided the UML Class diagram with the relevant parts (except for the interfaces, which I describe in code below). I was wondering if anyone had an idea on how to make this "better" architecture / class design. Also, actions that are very similar could be implemented in a near-future iteration. Code for interfaces public IActor1 { public Property1 { get; set; } public Property2 { get; set; } } public IActor2 { public Property3 { get; set; } public Property2 { get; set; } }

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  • Python Vector Class

    - by sfjedi
    I'm coming from a C# background where this stuff is super easy—trying to translate into Python for Maya. There's gotta' be a better way to do this. Basically, I'm looking to create a Vector class that will simply have x, y and z coordinates, but it would be ideal if this class returned a tuple with all 3 coordinates and if you could edit the values of this tuple through x, y and z properties, somehow. This is what I have so far, but there must be a better way to do this than using an exec statement, right? I hate using exec statements. class Vector(object): '''Creates a Maya vector/triple, having x, y and z coordinates as float values''' def __init__(self, x=0, y=0, z=0): self.x, self.y, self.z = x, y, z def attrsetter(attr): def set_float(self, value): setattr(self, attr, float(value)) return set_float for xyz in 'xyz': exec("%s = property(fget=attrgetter('_%s'), fset=attrsetter('_%s'))" % (xyz, xyz, xyz))

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  • Unbelievable: Cannot cast from class X to its super class

    - by Phuong Nguyen de ManCity fan
    I'm encountering a very weird problem with Spring (3.0.1.RELEASE), TestNG (5.11) and Maven Surefire (2.5). I have a test class that extends a Spring helper class for testNG so that test context can be loaded from an xml file (that contains some bean definitions). My project was imported into eclipse using m2eclipse (using Import Maven Project) The class run fine in Eclipse TestNG runner. However, it throws this exception with Maven Surefire Caused by: java.lang.ClassCastException: com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl cannot be cast to javax.xml.parsers.DocumentBuilderFactory at javax.xml.parsers.DocumentBuilderFactory.newInstance(DocumentBuilderFactory.java:123) at org.springframework.beans.factory.xml.DefaultDocumentLoader.createDocumentBuilderFactory(DefaultDocumentLoader.java:89) at org.springframework.beans.factory.xml.DefaultDocumentLoader.loadDocument(DefaultDocumentLoader.java:70) at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:388) I have eliminated all involved dependencies in my pom so that the two classes com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl and javax.xml.parsers.DocumentBuilderFactory are coming from JRE only (the rt.jar). So, it looks so unbelievable to me. I wonder if there is any mechanism in loading class that can explain for this behavior? Thanks.

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  • Change select's class based on selected option's class

    - by Alasdair
    I have a page that contains numerous <select> elements. What I'm trying to achieve is to ensure that if a <select>'s selected <option> has a class called italic, then the <select> then has the italic class added (i.e. jQuery.addClass('italic')). If it doesn't, then the italic class is removed from the <select> to ensure other <option> elements are displayed correctly (i.e. jQuery.removeClass('italic')). What I'm noticing with most of my attempts is that either all the <select> have the italic class or that the italic class isn't being removed accordingly. Since I'm unsure my choice in selectors and callback logic are particularly sound or good practice in this instance (as I've been frustratingly trying to make it work) I've decided not to include the code I used in previous attempts. Instead, refer to this small HTML & CSS example: .italic { font-style: italic; } <select id="foo" name="foo" size="1" <option value="NA" selected="selected" - Select - </option <option value="1"Bar</option <option value="2"Fu</option <option value="3"Baz</option </select Also, I am aware that not all browsers support CSS styling of <select> and <option>. The related J2EE web application will only ever be accessed via Firefox under a controlled environment.

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  • Dotnet website - class in one file can't access class in a different file

    - by bmutch
    I've inherited a web site I'm editing in dotnet and it won't compile because the class in one file (say class1.vb) refers to a class in another file (say class2) (like Dim m_c As class2) , but the compiler says "Type Class2 is not defined". when I look in the object browswer the classes are listed separately (i.e. not all grouped under the same namespace) and appear as: Public Class Class1 Inherits System.Object Member of C:...\mywebsite\ Help!, thanks.

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  • Inside a decorator-class, access instance of the class which contains the decorated method

    - by ifischer
    I have the following decorator, which saves a configuration file after a method decorated with @saveconfig is called: class saveconfig(object): def __init__(self, f): self.f = f def __call__(self, *args): self.f(object, *args) # Here i want to access "cfg" defined in pbtools print "Saving configuration" I'm using this decorator inside the following class. After the method createkvm is called, the configuration object self.cfg should be saved inside the decorator: class pbtools() def __init__(self): self.configfile = open("pbt.properties", 'r+') # This variable should be available inside my decorator self.cfg = ConfigObj(infile = self.configfile) @saveconfig def createkvm(self): print "creating kvm" My problem is that i need to access the object variable self.cfg inside the decorator saveconfig. A first naive approach was to add a parameter to the decorator which holds the object, like @saveconfig(self), but this doesn't work. How can I access object variables of the method host inside the decorator? Do i have to define the decorator inside the same class to get access?

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  • Invoke a subclass method of an anonymous class

    - by arjacsoh
    I am trying right now to dig into anonymous classes and one question was just arised I 'd prefer not to refer to much details and to pose my question straightforward: How can I invoke the method sizzle() in the following anonymous class: public class Popcorn { public void pop() { System.out.println("popcorn"); } } class Food { Popcorn p = new Popcorn() { public void sizzle() { System.out.println("anonymous sizzling popcorn"); } public void pop() { System.out.println("anonymous popcorn"); } }; public void popIt() { p.pop(); // OK, Popcorn has a pop() method p.sizzle(); // Not Legal! Popcorn does not have sizzle() } } It is known and definite in polymorphism rules that a refernce of a superclass cannot invoke methods of subclass without downcasting (even if it refers to an object of the given subclass). However in the above case what is the "key" to invoke the sizzle() method?

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  • Class to manage e-mail from iPhone

    - by Scott Pendleton
    I'm working on an iPhone app that offers the user the opportunity to send an e-mail in 3 different places in the app, and for 3 different purposes. Rather than put the same code for showing the e-mail composer in 3 different view controllers, shouldn't I develop a separate E-mail class, create an instance, and then set properties such as To, CC, BCC, Body, HTML_Or_Not, and so on? Also, if I create an instance of such a class, and it brings up the e-mail composer, is it OK to release the class even before the e-mail composer has left the screen?

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  • When to use a module, and when to use a class

    - by Matt Briggs
    I am currently working through the Gregory Brown Ruby Best Practices book. Early on, he is talking about refactoring some functionality from helper methods on a related class, to some methods on module, then had the module extend self. Hadn't seen that before, after a quick google, found out that extend self on a module lets methods defined on the module see each other, which makes sense. Now, my question is when would you do something like this module StyleParser extend self def process(text) ... end def style_tag?(text) ... end end and then refer to it in tests with @parser = Prawn::Document::Text::StyleParser as opposed to just using a class with some class methods on it? is it so that you can use it as a mixin? or are there other reasons I'm not seeing?

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  • Base class pointer vs inherited class pointer?

    - by Goose Bumper
    Suppose I have a class Dog that inherits from a class Animal. What is the difference between these two lines of code? Animal *a = new Dog(); Dog *d = new Dog(); In one, the pointer is for the base class, and in the other, the pointer is for the derived class. But when would this distinction become important? For polymorphism, either one would work exactly the same, right?

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  • Is a base class with shared fields and functions good design

    - by eych
    I've got a BaseDataClass with shared fields and functions Protected Shared dbase as SqlDatabase Protected Shared dbCommand as DBCommand ... //also have a sync object used by the derived classes for Synclock'ing Protected Shared ReadOnly syncObj As Object = New Object() Protected Shared Sub Init() //initializes fields, sets connections Protected Shared Sub CleanAll() //closes connections, disposes, etc. I have several classes that derive from this base class. The derived classes have all Shared functions that can be called directly from the BLL with no instantiation. The functions in these derived classes call the base Init(), call their specific stored procs, call the base CleanAll() and then return the results. So if I have 5 derived classes with 10 functions each, totaling 50 possible function calls, since they are all Shared, the CLR only calls one at a time, right? All calls are queued to wait until each Shared function completes. Is there a better design with having Shared functions in your DAL and still have base class functions? Or since I have a base class, is it better to move towards instance methods within the DAL?

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  • Php wrapper class for XML

    - by gms8994
    I'm working on a new class to wrap XML handling. I want my class to use simplexml if it's installed, and the built in XML functions if it's not. Can anyone give me some suggestions on a skeleton class to do this? It seems "wrong" to litter each method with a bunch of if statements, and that also seems like it would make it nearly impossible to correctly test. Any upfront suggestions would be great! EDIT: I'm talking about these built-in xml functions.

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  • Help naming a class that has a single public method called Execute()

    - by devoured elysium
    I have designed the following class that should work kind of like a method (usually the user will just run Execute()): public abstract class ??? { protected bool hasFailed = false; protected bool hasRun = false; public bool HasFailed { get { return hasFailed; } } public bool HasRun { get { return hasRun; } } private void Restart() { hasFailed = false; hasRun = false; } public bool Execute() { ExecuteImplementation(); bool returnValue = hasFailed; Restart(); return returnValue; } protected abstract void ExecuteImplementation(); } My question is: how should I name this class? Runnable? Method(sounds awkward)?

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  • C2664 when casting child class to templated parent class

    - by DC
    I have a parent class which is templated, and a child class which implements it. template< typename T1, typename T2> class ParentClass{ . . . }; class ChildClass : public ParentClass<MyT1, MyT2> { . . . }; And I want to have a pointer which I can use polymorphically: ParentClass<T1, T2>* ptr; ptr = static_cast<ParentClass<MyT1, MyT2>* >(new ChildClass() ); No matter how I cast it, I always get a C2664 which has the same expression: error C2664: cannot convert parameter 1 from 'ParentClass< T1,T2 *' to 'ParentClass< T1,T2 *' Is it not possible to cast pointer types between inherited types if the parent is templated, even if the types specified in the templates are the same?

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  • noncopyable static const member class in template class

    - by Dukales
    I have a non-copyable (inherited from boost::noncopyable) class that I use as a custom namespace. Also, I have another class, that uses previous one, as shown here: #include <boost/utility.hpp> #include <cmath> template< typename F > struct custom_namespace : boost::noncopyable { F sqrt_of_half(F const & x) const { using std::sqrt; return sqrt(x / F(2.0L)); } // ... maybe others are not so dummy const/constexpr methods }; template< typename F > class custom_namespace_user { static ::custom_namespace< F > const custom_namespace_; public : F poisson() const { return custom_namespace_.sqrt_of_half(M_PI); } static F square_diagonal(F const & a) { return a * custom_namespace_.sqrt_of_half(1.0L); } }; template< typename F > ::custom_namespace< F > const custom_namespace_user< F >::custom_namespace_(); this code leads to the next error (even without instantiation): error: no 'const custom_namespace custom_namespace_user::custom_namespace_()' member function declared in class 'custom_namespace_user' The next way is not legitimate: template< typename F ::custom_namespace< F const custom_namespace_user< F ::custom_namespace_ = ::custom_namespace< F (); What should I do to declare this two classes (first as noncopyable static const member class of second)? Is this feaseble?

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