Lesson 25 Static member variable of class

One 、 review

• Access to... By name public Member variables
• The variables of each object are exclusive
• Member variables cannot be shared between objects

Two 、 Static member variable

• stay C++ Static member variables can be defined in
• Static member variables belong to the entire class
• The life cycle of a static member variable does not depend on any object
• Common static member variables can be accessed directly through the class name
• All objects share static member variables of the class
• Common static member variables can be accessed through object names

characteristic

• Directly through when defining static Keyword modification
• Static member variables need to allocate space outside the class
• Static member variables are located in the global data area inside the program

Rule of grammar

type classname::varName = value;

 Example 
class test{
	private:
	static int t1;//  Static member functions 
};
int test::t1 = 0;//  You also need to define 

3、 ... and 、 Summary

• Class can be passed through static Keyword to define static member variables
• Static member variables belong to all classes
• Every object can access static member variables
• Static member variables allocate space in the global data area
• The lifetime of static member variables is the running time of the program