C ++:新手初始化程序列表问题 [英] C++: newbie initializer list question

问题描述

新手在这里.我正在查看公司代码.

Newbie here. I am looking at company code.

似乎在类A中没有成员变量，但是在类A的构造函数中，即使类A不包含任何类型B的成员变量(或根本不包含任何成员变量！)，它仍会初始化对象B.

It appears that there are NO member variables in class A yet in A's constructor it initializes an object B even though class A does not contain any member variable of type B (or any member variable at all!).

我想我什至不了解它，甚至不能问一个问题...所以这是怎么回事！?我的直觉是，在尝试初始化变量之前，您需要一个变量.在没有对象的情况下如何初始化对象(或有什么好处)?

I guess I don't understand it enough to even ask a question...so what's going on here!? My intuition is that you need a variable before you even try to initialize it. How is it possible (or what good does it do) to initialize an object without having the object?

.h:

class A: public B
{
public:
     A(bool r = true);
     virtual ~A;

private:
}

.cpp:

A::A(bool r) : B(r ? B::someEnumeration : B::anotherEnumeration)
{
}

A::~A()
{
}

请帮助.

谢谢， 杰布

推荐答案

Class A(公开)

Class A (publicly) inherits from class B:

class A: public B

用参数初始化基类的唯一方法是通过初始化程序列表.

The only way to initialize a base class with parameters is through the initializer list.

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