Android开发flow常见API的使用示例详解

public suspend inline fun <T> Flow<T>.collect(crossinline action: suspend (value: T) -> Unit): Unit =
    collect(object : FlowCollector<T> {
        override suspend fun emit(value: T) = action(value)
    })

fun main() {
    GlobalScope.launch {
        flow {
            emit("haha")
        }.collect {
        }
    }
}

public fun <T> Flow<T>.launchIn(scope: CoroutineScope): Job = scope.launch {
    collect() // tail-call
}

fun main() {
    flow {
        emit("haha")
    }.launchIn(GlobalScope)
}

public fun <T> Flow<T>.catch(action: suspend FlowCollector<T>.(cause: Throwable) -> Unit): Flow<T> =
    flow {
        val exception = catchImpl(this)
        if (exception != null) action(exception)
    }

public fun <T> merge(vararg flows: Flow<T>): Flow<T> = flows.asIterable().merge()

fun main() {
    GlobalScope.launch {
        merge(flow {
            delay(1000)
            emit(4)
        }, flow {
            println("flow2")
            delay(2000)
            emit(20)
        }).collect {
            println("collect value: $it")
        }
    }
}

public inline fun <T, R> Flow<T>.map(crossinline transform: suspend (value: T) -> R): Flow<R> = transform { value ->
   return@transform emit(transform(value))
}

fun main() {
    GlobalScope.launch {
        flow {
            emit(5)
        }.map {
            "ha".repeat(it)
        }.collect {
            println("collect value: $it")
        }
    }
}