类内部的static成员，除了为const static 且为整数类型（int char bool）可在类内部初始化。

其他的都建议在对应的cpp文件中进行初始化。

test.h

#ifndef TEST_H_INCLUDED#define TEST_H_INCLUDEDclass B {public:    B();    B(int a);    void print () const;};class A {public:    const static B a;    const static int x = 100;};#endif // TEST_H_INCLUDED

 

test.cpp

#include 
     
      #include "test.h"B::B() {    std::cout << "B construct" << std::endl;}B::B(int x) {    std::cout << "B construct x" << std::endl;}void B::print() const {    std::cout << "B print" << std::endl;}const B A::a(1);