[英]Kotlin: How to return a variable from within an asynchronous lambda?
I'm using fuel http to make a simple GET request. 我正在使用Fuel http发出简单的GET请求。 Here's my code:
这是我的代码:
fun fetchTweets(): List<Tweet> {
endpoint.httpGet(listOf("user" to "me", "limit" to 20))
.responseObject(Tweet.Deserializer()) { _, _, result ->
result.get().forEach { Log.i("TWEET", it.text) }
val tweets = result.get().toList() //I want to return this
}
}
If I do return tweets
just below val tweets
, I get an error: return is not allowed here
. 如果我确实在
val tweets
之下return tweets
,则会收到错误消息: return is not allowed here
。
The makes sense to me. 这对我来说很有意义。 But the question still remains, how do I write a function that returns the variable created within the lambda?
但是问题仍然存在,我该如何编写一个函数以返回在lambda中创建的变量? In this case, I want to return
tweets
在这种情况下,我想返回
tweets
You could pass a lambda to your method: 您可以将lambda传递给您的方法:
fun fetchTweets(
callback: (List<Tweet>) -> Unit
) {
endpoint.httpGet(listOf("user" to "me", "limit" to 20))
.responseObject(Tweet.Deserializer()) { _, _, result ->
result.get().forEach { Log.i("TWEET", it.text) }
val tweets = c.get().toList()
callback(tweets)
}
}
Using https://github.com/kittinunf/fuel/tree/master/fuel-coroutines you should be able to write something like (I am unfamiliar with the library, this is based just on the README example): 使用https://github.com/kittinunf/fuel/tree/master/fuel-coroutines,您应该可以编写如下内容(我不熟悉该库,这仅基于README示例):
suspend fun fetchTweets(): List<Tweet> {
val (_, _, result) = endpoint.httpGet(listOf("user" to "me", "limit" to 20))
.awaitObjectResponseResult(Tweet.Deserializer())
result.get().forEach { Log.i("TWEET", it.text) }
return c.get().toList()
}
(It isn't clear where c
comes from in your question; is that maybe a typo for result.get().toList()
?) (不清楚您的问题中
c
来源;这可能是result.get().toList()
的错字吗?)
If you are unfamiliar with coroutines, read https://kotlinlang.org/docs/reference/coroutines/coroutines-guide.html . 如果您不熟悉协程,请阅读https://kotlinlang.org/docs/reference/coroutines/coroutines-guide.html 。
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