在类中的方法正确使用`= delete` [英] Correct use of `= delete` for methods in classes

问题描述

下面的snipplet是否适用于取消定义一个类的所有其他方法和构造函数？

Is the following snipplet correct for un-defining all otherwise generated methods and constructors for a class?

struct Picture {

  // 'explicit': no accidental cast from string to Picture
  explicit Picture(const string &filename) { /* load image from file */ }

  // no accidental construction, i.e. temporaries and the like
  Picture() = delete;

  // no copy
  Picture(const Picture&) = delete;

  // no assign
  Picture& operator=(const Picture&) = delete;

  // no move
  Picture(Picture&&) = delete;

  // no move-assign
  Picture& operator=(Picture&&) = delete; // return type correct?
};

这会删除每个默认的编译器实现，只剩下析构函数，对吗？没有它，该类将是（几乎）不可用的，我想，但我可以删除它，正确吗？

This deletes every default compiler implementation and only leaves the destructor, right? Without it the class would be (almost) unusable I guess, but I could delete it as well, correct?

是返回类型 Picture& operator =（Picture&&）的是否正确？

Is the return type Picture& of the move-assign operator=(Picture&&) correct? Does it make a difference if I wrote Picture&& for the return type?

推荐答案

除了Xeo的回答：

是的，一切都是正确的。如果你想要，你可以消除所有删除的成员，但删除的副本构造函数和删除的副本分配，并具有相同的效果：

Yes, everything is correct. If you wanted you could eliminate all of the deleted members but the deleted copy constructor and deleted copy assignment and have the same effect:

struct Picture {  // Also ok

  // 'explicit': no accidental cast from string to Picture
  explicit Picture(const string &filename) { /* load image from file */ }

  // no copy
  Picture(const Picture&) = delete;

  // no assign
  Picture& operator=(const Picture&) = delete;
};

复制构造函数的显式声明禁止隐式生成默认构造函数，move constructor和move assignment成员。将这些成员明确删除是一个问题。有些人可能会看到它是好的文档。其他人可能会认为它过于冗长。

The explicit declaration of the copy constructor inhibits the implicit generation of the default constructor, move constructor and move assignment members. Having these members explicitly deleted is a matter of taste. Some will probably see it as good documentation. Others may see it as overly verbose.

这篇关于在类中的方法正确使用`= delete`的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！