温故而知新 - static应用

1> A static data member can be of the same class type as that of which it is a member. a nonstatic data member is restricted to being decleared as a pointer or a reference to an object of its class.

class Bar{
private:
static Bar mem1; //ok
Bar *mem2;  //ok
Bar mem3;   //error
}

2> static成员变量能够作为当前class的成员函数的默认参数，但是non-static则不可以

3>对于static成员函数的声明和定义，在class 中声明时要标注static关键字，而在class外部定义时，一定不要写static.

4>static 函数中要注意什么？

1. ·不能有this 指针
2. ·不能引用class中的非static成员(变量、成员)
3. ·static的成员函数不能再声明成volatile或const