c++ - 如何限制从主函数访问类函数？

Question

如何限制主函数对类函数的访问？

这是我的代码。

class Bar
{
public: void doSomething(){}
};

class Foo
{
public: Bar bar;
//Only this scope that bar object was declared(In this case only Foo class)
//Can access doSomething() by bar object.
};

int main()
{
    Foo foo;
    foo.bar.doSomething(); //doSomething() should be limited(can't access)
    return 0;
}

PS.抱歉我的英语不好。

---

编辑:我没有删除旧代码，而是使用新代码进行扩展。我认为这种情况不能使用 friend 类。因为我打算用于每堂课。谢谢

class Bar
{
public:
    void A() {} //Can access in scope that object of Bar was declared only
    void B() {}
    void C() {}
};

class Foo
{
public:
    Bar bar;
    //Only this scope that bar object was declared(In this case is a Foo class)
    //Foo class can access A function by bar object

    //main function need to access bar object with B, C function
    //but main function don't need to access A function
    void CallA()
    {
        bar.A(); //Correct
    }
};

int main()
{
    Foo foo;
    foo.bar.A(); //Incorrect: A function should be limited(can't access)    
    foo.bar.B(); //Correct
    foo.bar.C(); //Correct
    foo.CallA(); //Correct
    return 0;
}

Answer 1

让 Foo 成为 Bar 的 friend

class Bar
{
    friend class Foo;
private:
    void doSomething(){}
};

同时避免将成员变量设为public。使用 setters/getters 代替