什么时候应该使用std :: bind？ [英] When should I use std::bind?

问题描述

每次我需要使用 std :: bind ，我最终使用lambda。所以我应该什么时候使用 std :: bind ？我刚刚完成从一个代码库中删除它，我发现lambdas总是比 std :: bind 更简单和更清晰。是不是 std :: bind 完全不必要？不应该在将来被弃用吗？我应该在什么时候喜欢 std :: bind 到lambda函数？ （必须有一个理由，它与lambdas同时达到标准。）

Every time I need to use std::bind, I end up using a lambda instead. So when should I use std::bind? I just finished removing it from one codebase, and I found that lambdas were always simpler and clearer than std::bind. Isn't std::bind completely unnecessary? Shouldn't it be deprecated in the future? When should I prefer std::bind to lambda functions? (There has to be a reason that it got into the standard at the same time as lambdas.)

我也注意到越来越多的人熟悉lambdas （所以他们知道lambdas做什么）。但是，很少有人熟悉 std :: bind 和 std :: placeholders 。

I've also noticed that more and more people are familiar with lambdas (so they know what lambdas do). However, a lot fewer people are familiar with std::bind and std::placeholders.

推荐答案

这里是你不能用lambda做的事情：

Here's something you can't do with a lambda:

std::unique_ptr<SomeType> ptr = ...;
return std::bind(&SomeType::Function, std::move(ptr), _1, _2);

Lambdas无法捕获只移动类型;它们只能通过复制或通过左值引用捕获值。虽然不可否认，这是一个临时问题，正在积极解决C ++ 14;）

Lambdas can't capture move-only types; they can only capture values by copy or by lvalue reference. Though admittedly this is a temporary issue that's being actively resolved for C++14 ;)

更简单和更清晰是一个意见的问题。对于简单的绑定情况， bind 可以减少很多键入。 bind 也只专注于函数绑定，所以如果你看到 std :: bind 看着。如果你使用一个lambda，你必须看看lambda实现，以确定它是做什么。

"Simpler and clearer" is a matter of opinion. For simple binding cases, bind can take a lot less typing. bind also is focused solely on function binding, so if you see std::bind, you know what you're looking at. Whereas if you use a lambda, you have to look at the lambda implementation to be certain of what it does.

最后，C ++不会弃用的东西，只是因为一些其他功能可以做它做什么。 auto_ptr 已被弃用，因为它本身就是危险的，而且有一个非危险的替代方法。

Lastly, C++ does not deprecate things just because some other feature can do what it does. auto_ptr was deprecated because it is inherently dangerous to use, and there is a non-dangerous alternative.

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