如何从C ++中的子C中使用初始化超类参数？ [英] How can i initialize superclass params from within the child c-tor in C++?

问题描述

观察以下示例：

class A {
public:
    A(int param1, int param2, int param3) {
        // ...
    }
};

class B : public A {
public:
    B() : m_param1(1), m_param(2), m_param(3), A(m_param1, m_param2, m_param3) {
        // ...
    }
};

B b;

显然，当创建b时，A的ctor将在B的参数

Obviously, when "b" will be created, A's ctor will be called before the parameters of B will be initialized.

此规则禁止我创建简化类初始化的包装器类。

This rule prevents me from creating "wrapper" classes which simplify the class's initialization.

是这样做的正确方法？

感谢，
Amir

Thanks, Amir

我的具体情况下，参数不是原始的，这个例子只是帮助我解释自己。

PS: In my particular case, the parameters are not primitives, this example just helped me to explain myself.

推荐答案

参数不是基元。那么你有这样的东西吗？

"The parameters are not primitives". So you have something like this?

class Param { /*...*/ };
class A {
public:
  A(const Param& param1, const Param& param2, const Param& param3);
};

class B : public A {
public:
  B();
private:
  Param m_param1;
  Param m_param2;
  Param m_param3;
};

并且您要传递 B 到 A 的构造函数。这个怎么样？

And you want to pass the members of B to the constructor of A. How about this?

class B_params {
protected:
  B_params(int v1, int v2, int v3);
  Param m_param1;
  Param m_param2;
  Param m_param3;
};
class B : private B_params, public A {
public:
  B();
};

B_params::B_params(int v1, int v2, int v3)
  : m_param1(v1), m_param2(v2), m_param3(v3) {}
B::B() : B_params(1,2,3), A(m_param1, m_param2, m_param3) {}

只需确保 B 列表中的 B_params 在 A $ c>是继承的类。

Just make sure B_params comes before A in the list of B's inherited classes.

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