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  • Why can't I inherit static classes?

    - by User
    I have several classes that do not really need any state. From the organizational point of view, I would like to put them into hierarchy. But it seems I can't declare inheritance for static classes. Something like that: public static class Base { } public static class Inherited : Base { } will not work. Why have the designers of the language closed that possibility?

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  • Static variables in Java for a test oObject creator

    - by stevebot
    Hey, I have something like the following TestObjectCreator{ private static Person person; private static Company company; static { person = new Person() person.setName("Joe"); company = new Company(); company.setName("Apple"); } public Person createTestPerson(){ return person; } public Person createTestCompany(){ return company; } } By applying static{} what am I gaining? I assume the objects are singletons as a result. However, if I did the following: Person person = TestObjectCreator.createTestPerson(); person.setName("Jill"); Person person2 = TestObjectCreator.createTestPerson(); would person2 be named Jill or Joe?

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  • Obj-c categories in static library

    - by Vladimir
    Can you guide me how to properly link static library to iphone project. I use staic library project added to app project as direct dependency (target - general - direct dependecies) and all works OK, but categories. A category defined in static library is not working in app. So my question is how to add static library with some categories into other project? And in general, what is best practice to use in app project code from other projects?

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  • Static library woes in iPhone 3.x with categories and C libraries

    - by hgpc
    I have a static library (let's call it S) that uses a category (NSData+Base64 from MGTwitterEngine) and a C library (MiniZip wrapped by ZipArchive). This static library is used in an iPhone 3.x project (let's call it A). To be able to use the MiniZip library I included its files in project A as well as the static library S. If not I get compilation errors. Project A works fine on the simulator. When I run it on the device, I get unrecognized selector errors when the category is used. As pointed out here, it seems there's a linker bug that affects categories in iPhone 3.x (http://stackoverflow.com/questions/1147676/categories-in-static-library-for-iphone-device-3-0). The workaround is to add -all_load to the Other Linker Flags of the project that references the static library. However, if I do this then I get duplicate symbol errors because I included the MiniZip libraries in project A. A workaround is to include the category files in project A as well. If I do this, project A works well in the device, but fails to build on the simulator because of duplicate symbol errors. How should I set up project A to make it work on the simulator and the device with the same configuration?

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  • How to return Current Object in a Static function in PHP

    - by streetparade
    I neet access to current object in a static method. Code: protected static $name; public static function name($modulename) { self::$name = $modulename; } public function __call($name, $arguments) { $me = new test(self::$name); return $me->$name($arguments); } I want to be able to call method log in Log class. Like this echo Mods::name("Log")->log("test"); How do i do that?

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  • What are the use cases for this static reflection code?

    - by Maslow
    This is Oliver Hanappi's static reflection code he posted on stackoverflow private static string GetMemberName(Expression expression) { switch (expression.NodeType) { case ExpressionType.MemberAccess: var memberExpression = (MemberExpression)expression; var supername = GetMemberName(memberExpression.Expression); if (String.IsNullOrEmpty(supername)) return memberExpression.Member.Name; return String.Concat(supername, '.', memberExpression.Member.Name); case ExpressionType.Call: var callExpression = (MethodCallExpression)expression; return callExpression.Method.Name; case ExpressionType.Convert: var unaryExpression = (UnaryExpression)expression; return GetMemberName(unaryExpression.Operand); case ExpressionType.Parameter: return String.Empty; default: throw new ArgumentException("The expression is not a member access or method call expression"); } } I have the public wrapper methods: public static string Name<T>(Expression<Action<T>> expression) { return GetMemberName(expression.Body); } public static string Name<T>(Expression<Func<T, object>> expression) { return GetMemberName(expression.Body); } then added my own method shortcuts public static string ClassMemberName<T>(this T sourceType,Expression<Func<T,object>> expression) { return GetMemberName(expression.Body); } public static string TMemberName<T>(this IEnumerable<T> sourceList, Expression<Func<T,object>> expression) { return GetMemberName(expression.Body); } What are examples of code that would necessitate or take advantage of the different branches in the GetMemberName(Expression expression) switch? what all is this code capable of making strongly typed?

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  • Where to put constant strings in C++: static class members or anonymous namespaces

    - by stone
    I need to define some constant strings that will be used only by one class. It looks like I have three options: Embed the strings directly into locations where they are used. Define them as private static constant members of the class: //A.h class A { private: static const std::string f1; static const std::string f2; static const std::string f3; }; //A.cpp const std::string f1 = "filename1"; const std::string f2 = "filename2"; const std::string f3 = "filename3"; //strings are used in this file Define them in an anonymous namespace in the cpp file: //A.cpp namespace { const std::string f1 = "filename1"; const std::string f2 = "filename2"; const std::string f3 = "filename3"; } //strings are used in this file Given these options, which one would you recommend and why? Thanks.

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  • Best practise for overriding static classes

    - by maxp
    As it is not possible to override a static class in c#, if i want to override a method I generally define a delegate matching the signature of the static method, then modify the method along the lines of: public static void foo(int bar) { if (delegatename!=null) { delegatename.Invoke(bar); } else { //execute previous code as normal } } I feel a twinge of guilt, knowing this is a bit messy. Can anyone suggest a neater solution to this problem (other than rewriting the original structure)

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  • Set Static block in Right side in Magento site

    - by yogs
    Hi I am new for Magento and don't much knowledge of programing what i want to do is i heve three categories on my site and created three static blocks for it and set it up on middle of each category page with their related block all working fine but now i want to move it in Right Sidebar in My site so pls. suggest how and where do i change to display my Static block in Right sidebar Example : I have three Categories and three static block for each category : Womens,Mens,Kids - Static Bloks : womens_block,mens_block,kids_block now pls. suggest how can i move it to Right side of my page Above Shopping cart. Any help is appreciated Thanks in Advance.

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  • C# two classes with static members referring to each other

    - by Jerry
    Hi, I wonder why this code doesn't end up in endless recursion. I guess it's connected to the automatic initialization of static members to default values, but can someone tell me "step by step" how does 'a' get the value of 2 and 'b' of 1? public class A { public static int a = B.b + 1; } public class B { public static int b = A.a + 1; } static void Main(string[] args) { Console.WriteLine("A.a={0}, B.b={1}", A.a, B.b); //A.a=2, B.b=1 Console.Read(); }

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  • Uses for static generic classes?

    - by Hightechrider
    What are the key uses of a Static Generic Class in C#? When should they be used? What examples best illustrate their usage? e.g. public static class Example<T> { public static ... } Since you can't define extension methods in them they appear to be somewhat limited in their utility. Web references on the topic are scarce so clearly there aren't a lot of people using them. Here's a couple:- http://ayende.com/Blog/archive/2005/10/05/StaticGenericClass.aspx http://stackoverflow.com/questions/686630/static-generic-class-as-dictionary

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  • Variable declarations in header files - static or not?

    - by Rob
    When refactoring away some #defines I came across declarations similar to the following in a C++ header file: static const unsigned int VAL = 42; const unsigned int ANOTHER_VAL = 37; The question is, what difference, if any, will the static make? Note that multiple inclusion of the headers isn't possible due to the classic #ifndef HEADER #define HEADER #endif trick (if that matters). Does the static mean only one copy of VAL is created, in case the header is included by more than one source file?

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  • Static Property losing its value intermittently ?

    - by joedotnot
    Is there something fundamentally wrong with the following design, or can anyone see why would the static properties sometimes loose their values ? I have a class library project containing a class AppConfig; this class is consumed by a Webforms project. The skeleton of AppConfig class is as follows: Public Class AppConfig Implements IConfigurationSectionHandler Private Const C_KEY1 As String = "WebConfig.Key.1" Private Const C_KEY2 As String = "WebConfig.Key.2" Private Const C_KEY1_DEFAULT_VALUE as string = "Key1defaultVal" Private Const C_KEY2_DEFAULT_VALUE as string = "Key2defaultVal" Private Shared m_field1 As String Private Shared m_field2 As String Public Shared ReadOnly Property ConfigValue1() As String Get ConfigValue1= m_field1 End Get End Property Public Shared ReadOnly Property ConfigValue2() As String Get ConfigValue2 = m_field2 End Get End Property Public Shared Sub OnApplicationStart() m_field1 = ReadSetting(C_KEY1, C_KEY1_DEFAULT_VALUE) m_field2 = ReadSetting(C_KEY2, C_KEY1_DEFAULT_VALUE) End Sub Public Overloads Shared Function ReadSetting(ByVal key As String, ByVal defaultValue As String) As String Try Dim setting As String = System.Configuration.ConfigurationManager.AppSettings(key) If setting Is Nothing Then ReadSetting = defaultValue Else ReadSetting = setting End If Catch ReadSetting = defaultValue End Try End Function Public Function Create(ByVal parent As Object, ByVal configContext As Object, ByVal section As System.Xml.XmlNode) As Object Implements System.Configuration.IConfigurationSectionHandler.Create Dim objSettings As NameValueCollection Dim objHandler As NameValueSectionHandler objHandler = New NameValueSectionHandler objSettings = CType(objHandler.Create(parent, configContext, section), NameValueCollection) Return 1 End Function End Class The Static Properties get set once on application start, from the Application_Start event of the Global.asax Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs) //Fires when the application is started AppConfig.OnApplicationStart() End Sub Thereafter, whenever we want to access a value in the Web.Config from anywhere, e.g. aspx page code-behind or another class or referenced class, we simply call the static property. For example, AppConfig.ConfigValue1() AppConfig.ConfigValue2() This is turn returns the value stored in the static backing fields m_field1, m_field2 Problem is sometimes these values are empty string, when clearly the Web.Config entry has values. Is there something fundamentally wrong with the above design, or is it reasonable to expect the static properties would keep their value for the life of the Application session?

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  • What effect does static const have on a namespace member

    - by user144182
    namespace MyNamespace { static const double GasConstant = 1.987; Class MyClass { // constructors, methods, etc. }; }; I previously had GasConstant declared within the MyClass declaration (and had a separate definition in the source file since C++ does not support const initialization of non-integral types). I however need to access it from other files and also logically it seems like it should reside at the namespace level. My questions is, what effect does static const have in this case? Clearly const means I can't assign a new value to GasConstant, but what does a static member at the namespace mean. Is this similar to filescope static effect, where the member is not accessible outside of the unit?

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  • what is the exact difference between PHP static class and singleton class

    - by Saif Bechan
    I have always used a Singleton class for a registry object in PHP. As all Singleton classes I think the main method looks like this: class registry { public static function singleton() { if( !isset( self::$instance ) ) { self::$instance = new registry(); } return self::$instance; } public function doSomething() { echo 'something'; } } So whenever I need something of the registry class I use a function like this: registry::singleton()->doSomethine(); Now I do not understand what the difference is between creating just a normal static function. Will it create a new object if I just use a normal static class. class registry { public static function doSomething() { echo 'something'; } } Now I can just use: registry::doSomethine(); Can someone explain to me what the function is of the singleton class. I really do not understand this.

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  • how to deal with a static analyzer output

    - by Jim
    We have started using a static analyzer (Coverity) on our code base. We were promptly stupefied by the sheer amount of warnings we received (its in the hundreds of thousands) , it will take the entire team a few mounts to clear them all (obliviously impossible). the options we discussed so far are 1) hire a contractor to sort out the warning and fix them - he drawback: we will probably need very experiences people to do all these modifications, and no contractor will have required understanding of the code. 2) filter out the warning and deal only with the dangerous ones - the problem here is that our static analysis output will always be cluttered by warning making it difficult for us to isolate problems. also the filtering of the warning is also a major effort. either way, bringing our code to a state when the static analyzer can be a useful tool for us seems a monumental task. so how is it possible to work with the static analyzer without braining current development efforts into a complete stand still?

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  • static const C++ class member initialized gives a duplicate symbol error when linking

    - by Petruza
    I have a class which has a static const array, it has to be initialized outside the class: class foo{ static const int array[3]; }; const int foo::array[3] = { 1, 2, 3 }; But then I get a duplicate symbol foo::array in foo.o and main.o foo.o hold the foo class, and main.o holds main() and uses instances of foo. How can I share this static const array between all instances of foo? I mean, that's the idea of a static member.

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  • Odd C++ template behaviour with static member vars

    - by jon hanson
    This piece of code is supposed to calculate an approximation to e (i.e. the mathematical constant ~ 2.71828183) at compile-time, using the following approach; e1 = 2 / 1 e2 = (2 * 2 + 1) / (2 * 1) = 5 / 2 = 2.5 e3 = (3 * 5 + 1) / (3 * 2) = 16 / 6 ~ 2.67 e4 = (4 * 16 + 1) / (4 * 6) = 65 / 24 ~ 2.708 ... e(i) = (e(i-1).numer * i + 1) / (e(i-1).denom * i) The computation is returned via the result static member however, after 2 iterations it yields zero instead of the expected value. I've added a static member function f() to compute the same value and that doesn't exhibit the same problem. #include <iostream> #include <iomanip> // Recursive case. template<int ITERS, int NUMERATOR = 2, int DENOMINATOR = 1, int I = 2> struct CalcE { static const double result; static double f () {return CalcE<ITERS, NUMERATOR * I + 1, DENOMINATOR * I, I + 1>::f ();} }; template<int ITERS, int NUMERATOR, int DENOMINATOR, int I> const double CalcE<ITERS, NUMERATOR, DENOMINATOR, I>::result = CalcE<ITERS, NUMERATOR * I + 1, DENOMINATOR * I, I + 1>::result; // Base case. template<int ITERS, int NUMERATOR, int DENOMINATOR> struct CalcE<ITERS, NUMERATOR, DENOMINATOR, ITERS> { static const double result; static double f () {return result;} }; template<int ITERS, int NUMERATOR, int DENOMINATOR> const double CalcE<ITERS, NUMERATOR, DENOMINATOR, ITERS>::result = static_cast<double>(NUMERATOR) / DENOMINATOR; // Test it. int main (int argc, char* argv[]) { std::cout << std::setprecision (8); std::cout << "e2 ~ " << CalcE<2>::result << std::endl; std::cout << "e3 ~ " << CalcE<3>::result << std::endl; std::cout << "e4 ~ " << CalcE<4>::result << std::endl; std::cout << "e5 ~ " << CalcE<5>::result << std::endl; std::cout << std::endl; std::cout << "e2 ~ " << CalcE<2>::f () << std::endl; std::cout << "e3 ~ " << CalcE<3>::f () << std::endl; std::cout << "e4 ~ " << CalcE<4>::f () << std::endl; std::cout << "e5 ~ " << CalcE<5>::f () << std::endl; return 0; } I've tested this with VS 2008 and VS 2010, and get the same results in each case: e2 ~ 2 e3 ~ 2.5 e4 ~ 0 e5 ~ 0 e2 ~ 2 e3 ~ 2.5 e4 ~ 2.6666667 e5 ~ 2.7083333 Why does result not yield the expected values whereas f() does? According to Rotsor's comment below, this does work with GCC, so I guess the question is, am i relying on some type of undefined behaviour with regards to static initialisation order, or is this a bug with Visual Studio?

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  • Serving CSS from a static domain

    - by Saif Bechan
    I want to serve my css and images from a static cookieless domain. Now my problem is how to point to the images from within my css files. I don't want to program my domain hard within the css file, for example: http://static.com/image.png I would rather have a variable pointing to the the image, so it works for every static domain i use. What is the best way for achieving this. Should i run the whole css file trough php and add the static domain in front of all the png references. A downside in this is that i have to place the whole css in html. Or is there another more optimized way of doing this.

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  • Java: when to use static methods

    - by KP65
    Hello, I am wondering when to use static methods? Say If i have a class with a few getters and setters, a method or two, and i want those methods only to be invokable on an instance object of the class. Does this mean i should use a static method? e.g Obj x = new Obj(); x.someMethod or Obj.someMethod (is this the static way?) I'm rather confused!

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  • .NET Reflection: How to call method of interface without creating instance?

    - by jitm
    I have situation where I have to call method of interface using reflection, like this object x = null; MethodInfo method = interfaceExists.GetMethod("ShutDown"); method.Invoke(x, new object[] { 4 }) As you can see I do not create instance of object! And, as I can supposed, I receive exception Non-static method requires a target And Question, Can I call method of interface using reflection without creating instance of interface and if YES, How I can do it ?

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  • What's static function for in c?

    - by user198729
    I only see static methods by which we don't need to instantiate a class to call the method. What's the purpose of a static function? static GtkWidget * create_bbox (gint horizontal, char *title, gint spacing, gint layout) { ... }

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  • Why can't you call a non-static method from a static method?

    - by VoodooChild
    I have a static method [Method1] in my class, which calls another method [Method2] in the same class and is not a static method. But this is a no-no. I get this error: An object reference is required for the non-static field, method, or property "ClassName.MethodName()" Can someone please briefly describe why? including other things that might be related to this.

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  • static, define, and const in C

    - by yCalleecharan
    Hi, I've read that static variables are used inside function when one doesn't want the variable value to change/initialize each time the function is called. But what about defining a variable static in the main program before "main" e.g. #include <stdio.h> static double m = 30000; int main(void) { value = m * 2 + 3; } Here the variable m has a constant value that won't get modified later in the main program. In the same line of thought what difference does it make to have these instead of using the static definition: const double m = 30000; or #define m 30000 //m or M and then making sure here to use double operations in the main code so as to convert m to the right data type. Thanks a lot...

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