kotlin - Kotlin是否按顺序等待参数？

Question

Kotlin是否严格按照顺序等候

receiver.await()

msg.await()

在第7行:

 suspend fun sendEmail(r: String, msg: String): Boolean { //(6)
        delay(2000)
        println("Sent '$msg' to $r")
        return true
    }

    suspend fun getReceiverAddressFromDatabase(): String { //(4)
        delay(1000)
        return "coroutine@kotlin.org"
    }

    suspend fun sendEmailSuspending(): Boolean {
        val msg = async(CommonPool) {             //(3)
            delay(500)
            "The message content"
        }
        val recipient = async(CommonPool) {  //(5)
            getReceiverAddressFromDatabase()  
        } 
        println("Waiting for email data")
        val sendStatus = async(CommonPool) {
            sendEmail(recipient.await(), msg.await()) //(7)
        }
        return sendStatus.await() //(8)
    }

或以任何顺序？我的意思是说Kotlin会先检查是否有receive.await()，然后才完成对msg.await()的检查？

Answer 1

您的问题不是await特定的，而是更深入地探讨了Kotlin本身的评估顺序语义。

因此，这是Kotlin language specification的报价:

Function arguments are then evaluated in the order of their appearance in the function call left-to-right

应用于您的代码行:

sendEmail(recipient.await(), msg.await())

很显然，首先评估 recipient.await()，然后评估 msg.await()。直到相关的 await()完成后， Deferred调用才会完成。