static-variables

问题 What is the difference between a static and instance variable. The following sentence is what I cant get: In certain cases, only one copy of a particular variable should be shared by all objects of a class- here a static variable is used. A static variable represents class wide info.All objects of a class share the same data. I thought that instance vars were used class wide whereas static variables only had scope within their own methods? 回答1: In the context of class attributes, static has a

问题 For static member variables in C++ class - the initialization is done outside the class. I wonder why? Any logical reasoning/constraint for this? Or is it purely legacy implementation - which the standard does not want to correct? I think having initialization in the class is more \"intuitive\" and less confusing.It also gives the sense of both static and global-ness of the variable. For example if you see the static const member. 回答1: Fundamentally this is because static members must be

问题 When I use static variables in C++, I often end up wanting to initialize one variable passing another to its constructor. In other words, I want to create static instances that depend on each other. Within a single .cpp or .h file this is not a problem: the instances will be created in the order they are declared. However, when you want to initialize a static instance with an instance in another compilation unit, the order seems impossible to specify. The result is that, depending on the

问题 How are unnamed namespaces superior to the static keyword? 回答1: You're basically referring to the section $7.3.1.1/2 from the C++ Standard, The use of the static keyword is deprecated when declaring objects in a namespace scope; the unnamed-namespace provides a superior alternative. Unnamed namespace is superior to static keyword, primarily because the keyword static applies only to the variables declarations and functions, not to the user-defined types . The following code is valid in C++ /

问题 I have searched about static variables in C#, but I am still not getting what its use is. Also, if I try to declare the variable inside the method it will not give me the permission to do this. Why? I have seen some examples about the static variables. I\'ve seen that we don\'t need to create an instance of the class to access the variable, but that is not enough to understand what its use is and when to use it. Second thing class Book { public static int myInt = 0; } public class Exercise {