C++ 私有扩展后转 public 一个变量

Question

疑惑如题：

加上class如下：

class A
{
public:
    int a;
    int b;
    int c;

    function1();
    function2();
}

和一个class B扩展A，如何从A转public所有变量？

class B : private A
{
public:
    int a; //How to turn this public from A
    int b; //How to turn this public from A
    int c; //How to turn this public from A
}

Answer 1

使用其他继承选项

  class B: public A

读这个Difference between private, public, and protected inheritance

Answer 2

不要在 B 中重新声明它们。

示例：

class A {
public:
    int a;
    int b;
    int c;

    void function1() {  }
    void function2() {  }
};

// Use private inheritance
class B : private A {
public:
    using A::a;
    using A::b;
    using A::c;

private:
    void function3()
    {
        // 'a' exists here, as it is defined public in base class A
    }
};

int main()
{
    B b;
    b.a = 1;

    b.function1(); // error: ‘A’ is not an accessible base of ‘B’

    return 0;
}

Answer 3

将私有基础 class 的 public 数据和成员公开为派生 class 中的 public 数据是一个坏主意。但是，如果必须，您可以使用：

class B : private A
{
   public:
      using A::a;
      using A::b;
      using A::c;
};

Answer 4

我觉得你可以

class B : private A
{
public:
    int A::a; 
    int A::b; 
    int A::c; 
}

不过，我没试过；

C++ 私有扩展后转 public 一个变量

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