在 lambda 函数中使用 auto self(shared_from_this()) 变量的原因是什么?

What#39;s the reason of using auto self(shared_from_this()) variable in lambda function?(在 lambda 函数中使用 auto self(shared_from_this()) 变量的原因是什么?)

问题描述

我阅读了 boost asio http 服务器示例代码(参见 http://www.boost.org/doc/libs/1_54_0/doc/html/boost_asio/example/cpp11/http/server/connection.cpp) 并找到 auto self(shared_from_this()); 变量被用于捕获范围([this, self]).但是在 lambda 函数中没有使用 self 变量.那么这样做有什么好处呢?

I read the boost asio http server example code (see http://www.boost.org/doc/libs/1_54_0/doc/html/boost_asio/example/cpp11/http/server/connection.cpp) and find the auto self(shared_from_this()); variable is been used in the capture scope ([this, self]). But the self variable is not been used in the lambda function. Then what's the benefit of doing so?

推荐答案

这样做是为了确保 connection 对象比异步操作寿命更长:只要 lambda 是活动的(即异步操作正在进行)，connection 实例也处于活动状态.

This is done in order to make sure that connection object outlives the asynchronous operation: as long as the lambda is alive (i.e. the async. operation is in progress), the connection instance is alive as well.

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