仅返回更快协程的值 [英] Return value only of the faster coroutine

问题描述

如何并行运行多个协程并仅返回最先完成的协程的值?

How can I run multiple coroutines in parallel and return only the value of the one that finishes first?

在现实生活中，我有两个数据源-数据库和 API服务.我不在乎数据从哪里来，我只需要快速.

Real-life scenario, I have two data sources - Database and API service. I don't care where does the data originate from, I just need it fast. How can I query both Database and API service and cancel the other request when the one finishes?

在RxJava世界中，这等于 Amb运算符.如何使用协程实现类似的行为?

In RxJava world this would be equal to Amb operator. How can I achieve similar behaviour using coroutines?

推荐答案

我想出了以下实现:

suspend fun getFaster(): Int = coroutineScope {
    select<Int> {
        async { getFromServer() }.onAwait { it }
        async { getFromDB() }.onAwait { it }
    }.also {
        coroutineContext.cancelChildren()
    }
}

coroutineScope充当其中执行的所有异步调用的父级. select完成后，我们可以取消其余部分.

The coroutineScope acts as a parent to all async calls performed within. After the select finishes we can just cancel the rest.

这篇关于仅返回更快协程的值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！