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< C++完整教學目錄 >

 C++提供一種方法，使類別A可以存取類別B放在private區域的類別成員。

中文翻譯做：友情宣告(friend declaration)。範例如：

class girl

{

public:

girl(string name_,int age_,int s)

{name=name_;age=age_;sweet_score=s;} 

friend class boy;   //宣告類別boy為友情類別     

private:

string name;

int age;

int sweet_score;

};

class boy

{

public:

boy(string name_,int age_){name=name_;age=age_;} 

void select(girl g1,girl g2){  //因為類別boy是類別girl的友情類別，所以可以存取類別girl放在private的類別成員

int like1=g1.sweet_score-g1.age;

int like2=g2.sweet_score-g2.age;

if(like1>like2)

{cout<<name<<" like "<<g1.name<<" more than "<<g2.name<<"!!"<<endl;}

else if(like2>like1)

{cout<<name<<" like "<<g2.name<<" more than "<<g1.name<<"!!"<<endl;}

else if(like1==like2)

{cout<<"cannot make decision!!"<<endl;}

}   

private:

string name;

int age;

};

void main() //主程式

{  

boy boy1("Jack",35);

girl girl1("wiewei",18,80);

girl girl2("nunu",22,85);

boy1.select(girl1,girl2); //顯示 Jack like nunu more than weiwei!!

}

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