- 静态成员变量

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int GenerateID()
{
    static int s_nID = 0;
    return s_nID++;
}
 
int main()
{
    std::cout << GenerateID() << std::endl;
    std::cout << GenerateID() << std::endl;
    std::cout << GenerateID() << std::endl;
    return 0;

This program prints:

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Note that s_nID has kept it’s value across multiple function calls.

The static keyword has another meaning when applied to global variables — it changes them from global scope to file scope. Because global variables are typically avoided by competent programmers, and file scope variables are just global variables limited to a single file, the static keyword is typically not used in this capacity.

Static member variables

C++ introduces two new uses for the static keyword when applied to classes: static member variables, and static member classes. Before we go into the static keyword as applied to member variables, first consider the following class: