如何限制从主函数访问类函数？

Question

如何限制从主函数访问类函数？

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。对不起，我英语不好。

---

编辑 ：我没有删除旧代码，但我扩展了新代码。 我认为这种情况不能使用好友类。 因为我计划将其用于所有课程。 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的朋友

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

并且避免public成员变量。 使用setters/getters代替

Answer 2

您可以将Foo定义为Bar的朋友类，并将doSomething（）设为私有。

Answer 3

在Foo内部将Bar bar Foo私有可以解决问题，不是吗？ 然后只有Foo类可以使用bar 。