Question

Code

 static void MyClass::ThreadEntryStatic()
 {
    //...
 }

 void MyClass::Begin()
 {
         CreateThread(..,ThreadEntryStatic,..);
 }

In which condition we should use the static in class ?

Answer 1

There are three places that the keyword static can be used. One is in the declaration of a struct/class when that context means that the method is a class method instead of an instance method. This means that this method is called directly and you don’t need an instance. From this static method, you can not access instance variables.

In MyClass.h

struct MyClass
{
  static void ThreadEntryStatic();

  void Begin();
};

In MyClass.cpp

void MyClass::ThreadEntryStatic()
{
}

void MyClass::Begin()
{
  CreateThread(.., MyClass::ThreadEntryStatic, ...);
}

A second case where the static keyword is use is in the scope of a file where you don’t want the visibility of the variable declared to be visible outside the file. You can also use an anonymous namespace for this as well.

A third case where the static keyword is used is in the scope of a method and the value is retained between executions of the function (and initialized with the assignment the first time).