编译出错,未找到B的定义,在使用一个类时,必须找到类的定义,或者使用如下三种方法
1. 使用指针 B*b;
2. 使用引用B& b;
3. 类分成头文件,互相包含
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class A
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{
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B b;
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}
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class B
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{
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}
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//a.h
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#ifndef A_H
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#define A_H
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#include "B.h"
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class A
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{
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public:
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A(){}
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A(B* pB):m_pB(pB) {}
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void useB();
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private:
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B* m_pB;
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};
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#endif
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//a.cc
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#include "A.h"
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void A::useB()
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{
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}
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//b.h
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#ifndef B_H
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#define B_H
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class A;
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class B
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{
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public:
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B(A* pA):m_pA(pA) {}
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void useA();
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private:
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A* m_pA;
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};
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#endif
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//b.cc
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#include "A.h"
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#include "B.h"
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void B::useA()
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{
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//do something for m_pA
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}
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//main.cc
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#include "a.h"
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#include "b.h"
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int main()
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{
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A *a = new A;
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a->useB();
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B *b = new B(a);
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b->useA();
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delete b;
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delete a;
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return 0;
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}
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