Kotlin 协程延迟不适用于 IOS 队列调度程序

Question

我有一个 KMM 应用，并且有代码：

fun getWeather(callback: (WeatherInfo) -> Unit) {
        println("Start loading")
        GlobalScope.launch(ApplicationDispatcher) {
            while (true) {
                val response = httpClient.get<String>(API_URL) {
                    url.parameters.apply {
                        set("q", "Moscow")
                        set("units", "metric")
                        set("appid", weatherApiKey())
                    }
                    println(url.build())
                }
                val result = Json {
                    ignoreUnknownKeys = true
                }.decodeFromString<WeatherApiResponse>(response).main
                callback(result)

                // because ApplicationDispatcher on IOS do not support delay
                withContext(Dispatchers.Default) { delay(DELAY_TIME) }
            }
        }
    }

如果我将withContext(Dispatchers.Default) { delay(DELAY_TIME) } 替换为delay(DELAY_TIME) 执行将永远不会返回到while 循环，它只会进行一次迭代。

而 IOS 的 ApplicationDispatcher 看起来像：

internal actual val ApplicationDispatcher: CoroutineDispatcher = NsQueueDispatcher(dispatch_get_main_queue())

internal class NsQueueDispatcher(
    private val dispatchQueue: dispatch_queue_t
) : CoroutineDispatcher() {
    override fun dispatch(context: CoroutineContext, block: Runnable) {
        dispatch_async(dispatchQueue) {
            block.run()
        }
    }
}

从delay 源代码我可以猜到，DefaultDelay 应该被返回并且应该有类似的行为有/没有withContext(Dispatchers.Default)

/** Returns [Delay] implementation of the given context */
internal val CoroutineContext.delay: Delay get() = get(ContinuationInterceptor) as? Delay ?: DefaultDelay

谢谢！

附：我从ktor-samples 得到ApplicationDispatcher。

Answer 1

可能ApplicationDispatcher是老东西了，你不用再用了：

CoroutineScope(Dispatchers.Default).launch {

}

或

MainScope().launch {

}

别忘了使用-native-mt 版本的协程，更多信息请看issue