C ++需要你从它的派生类初始化基类成员吗？ [英] Does C++ require you to initialize base class members from its derived class?

问题描述

class Base {
public:
    int a;
    Base():a(0) {}
    virtual ~Base();
}
class Derived : public Base {
public:
    int b;
    Derived():b(0) {
        Base* pBase = static_cast<Base*>(this);
        pBase->Base();
    }
    ~Derived();
}

是否需要调用基类构造函数，还是c ++会自动执行此操作吗？例如
C ++要求你从任何派生类初始化基类成员？

Is the call to the base class constructor necessary or does c++ do this automatically? e.g. Does C++ require you to initialize base class members from any derived class?

推荐答案

基类的构造函数会自动在派生类的构造函数被调用之前调用。

The base class's constructor will automatically be called before the derived class's constructor is called.

您可以使用初始化列表明确指定要调用的基础构造函数（如果有多个）：

You can explicitly specify which base constructor to call (if it has multiple) using initialization lists:

class Base {
  public:
    int a;
    Base():a(0) {}
    Base(int a):a(a) {}
};
class Derived {
  public:
    int b;
    Derived():Base(),b(0) {}
    Derived(int a):Base(a),b(0) {}
};

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