什么是“默认”意味着在类的函数声明之后？ [英] What does "default" mean after a class' function declaration?

问题描述

我已经在类中的函数声明旁边看到 default 。它是做什么的？

I've seen default used next to function declarations in a class. What does it do?

class C {
  C(const C&) = default;
  C(C&&) = default;
  C& operator=(const C&) & = default;
  C& operator=(C&&) & = default;
  virtual ~C() { }
};

推荐答案

这是一个新的C ++ 11功能。

这意味着您要使用编译器生成的该函数版本，所以你不需要指定一个body。

It means that you want to use the compiler-generated version of that function, so you don't need to specify a body.

你也可以使用 = delete 指定您不要希望编译器自动生成该函数。

You can also use = delete to specify that you don't want the compiler to generate that function automatically.

通过引入move构造函数和移动赋值运算符，当生成自动版本的构造函数，析构函数和赋值运算符时的规则变得相当复杂。使用 = default 和 = delete 使事情变得更容易，因为您不需要记住规则：你想要发生。

With the introduction of move constructors and move assignment operators, the rules for when automatic versions of constructors, destructors and assignment operators are generated has become quite complex. Using = default and = delete makes things easier as you don't need to remember the rules: you just say what you want to happen.

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