调用超类构造函数的规则是什么？ [英] What are the rules for calling the superclass constructor?

问题描述

从子类1调用超类构造函数的C ++规则是什么？

What are the C++ rules for calling the superclass constructor from a subclass one?

例如，我知道在Java中，你必须将它作为第一行子类构造函数（如果不这样做，则假定对no-arg超级构造函数进行隐式调用 - 如果缺少，则会给出编译错误。）

For example, I know in Java, you must do it as the first line of the subclass constructor (and if you don't, an implicit call to a no-arg super constructor is assumed - giving you a compile error if that's missing).

推荐答案

如果没有参数，则会自动为您调用基类构造函数。如果要使用参数调用超类构造函数，则必须使用子类的构造函数初始化列表。与Java不同，C ++支持多重继承（无论好坏），因此必须按名称引用基类，而不是super（）。

Base class constructors are automatically called for you if they have no argument. If you want to call a superclass constructor with an argument, you must use the subclass's constructor initialization list. Unlike Java, C++ supports multiple inheritance (for better or worse), so the base class must be referred to by name, rather than "super()".

class SuperClass
{
    public:

        SuperClass(int foo)
        {
            // do something with foo
        }
};

class SubClass : public SuperClass
{
    public:

        SubClass(int foo, int bar)
        : SuperClass(foo)    // Call the superclass constructor in the subclass' initialization list.
        {
            // do something with bar
        }
};

有关构造函数初始化列表的更多信息这里和这里。

More info on the constructor's initialization list here and here.

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