如何在 Rust 中重载赋值操作? [英] How can I overload the assignment operation in Rust?

问题描述

std::ops，但没有什么可用于简单的赋值.

There are lots of operations in std::ops, but there is nothing for a simple assignment.

我来自 C++ 背景，那里有复制构造函数和赋值运算符重载为您完成工作.我在 Rust 中需要类似的东西.

I'm coming from a C++ background, where there are copy constructor and assignment operator overloading that do the work for you. I need something like that in Rust.

推荐答案

你不能重载赋值.将变量从一个位置移动到另一个位置是 Rust 所有权语义的核心组成部分，并且是不可覆盖的.

You cannot overload assignment. Moving a variable from one location to another is a core component of Rust's ownership semantics and is not overridable.

另一个答案建议您自定义实现 Copy 特性.这是没有意义的，因为没有什么可实现的:

Another answer suggests that you custom-implement the Copy trait. This makes no sense, as there's nothing to implement:

pub trait Copy: Clone { }

你可以实现Clone 对于一个类型，但要使用 clone 你必须显式调用它:

You could implement Clone for a type, but to use clone you have to call it explicitly:

let foo = bar.clone();

实际赋值仍然只是将位从右侧复制到左侧，唯一的区别是您没有放弃对 bar.

The actual assignment is still just copying bits from the right-hand side to the left-hand side, the only difference is that you don't give up ownership of bar.

如果您的类型可以通过简单地复制位来复制，那么实现Copy是合适的.如果可以通过执行某种函数来复制它，那么实现Clone是合适的.我不知道在任何给定的类型分配中隐式执行代码(我认为这是一件好事).

If your type can be duplicated by simply copying bits, then it's appropriate to implement Copy. If it can be duplicated by executing some kind of function, then it's appropriate to implement Clone. There is no way I know of to implicitly execute code at any given assignment of a type (and I count that as a good thing).

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