C ++ const方法对非常量指针成员 [英] C++ const method on non const pointer member

问题描述

我想知道如何通过const方法保护非const指针成员从一个对象。例如：

I was wondering how protect a non const pointer member from an object throught a const method. For example:

class B{
    public:
        B(){
            this->val=0;
        }

        void setVal(){
            this->val = 2;
        }

    private:
        int val;
};

class A{
    public:
        A():b(new B){}
        void changeMemberFromConstMethod() const{
            this->b->setVal();
        }
    private:
        B * b; // how to protect data pointed in A::changeMemberFromConstMethod
}

保护A :: b从他的方法指向的数据？
经过许多网络研究，尚未找到满意的答复。

Is it possible to "protect" A::b data pointed from his method? After many research on web, no satisfied reponse found yet.

感谢您的帮助。

推荐答案

这样的东西，可能是：

template <typename T>
class deep_const_ptr {
  T* p_;
public:
  deep_const_ptr(T* p) : p_(p);

  T* operator->() { return p_;}
  const T* operator->() const { return p_;}
};

class A {
  deep_const_ptr<B> b = new B;
};

deep_const_ptr 在的一个的const方法，并像 T * const T * const >在非const方法中。进一步丰富课程将留给读者。

deep_const_ptr behaves like a const T* const pointer in A's const methods, and like T* in non-const methods. Fleshing the class out further is left as an exercise for the reader.

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