在lambda中使用return吗? [英] Using return inside a lambda?

问题描述

在下面的代码中，如果行程为空，我想显示我的空视图，然后返回并避免运行下面的代码，但是编译器说此处不允许返回".

In the code below, I want to show my empty views if trips is empty and then return and avoid running the below code, but the compiler says "return is not allowed here".

mainRepo.fetchUpcomingTrips { trips ->
    if (trips.isEmpty()) {
        showEmptyViews()
        return
    }

    // run some code if it's not empty
}

有没有办法像这样返回?

Is there a way to return like that?

我知道我可以将它放在if else块中，但我讨厌编写if else块，在有更多条件的情况下，我认为它不太容易理解.

I know I can just put it in an if else block but I hate writing if else's, it's less understandable/readable in my opinion when there's a few more conditions.

推荐答案

只需使用限定的返回语法:return@fetchUpcomingTrips.

Just use the qualified return syntax: return@fetchUpcomingTrips.

在Kotlin中，lambda内的return表示从最里面的嵌套fun返回(忽略lambda)，并且在非

In Kotlin, return inside a lambda means return from the innermost nesting fun (ignoring lambdas), and it is not allowed in lambdas that are not inlined.

return@label语法用于指定要返回的范围.您可以使用将lambda传递给(fetchUpcomingTrips)的函数的名称作为标签:

The return@label syntax is used to specify the scope to return from. You can use the name of the function the lambda is passed to (fetchUpcomingTrips) as the label:

mainRepo.fetchUpcomingTrips { trips ->
    if (trips.isEmpty()) {
        showEmptyViews()
        return@fetchUpcomingTrips 
    }

    // ...
}

相关:

• 返回标签 在语言参考中

• Return at labels in the language reference

"return @"是什么意思?

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