从表达式中断或返回

Question

我想做什么:

when(transaction.state) {
    Transaction.Type.EXPIRED,
    //about 10 more types
    Transaction.Type.BLOCKED -> {
        if (transaction.type == Transaction.Type.BLOCKED && transaction.closeAnyway) {
            close(transaction)
            break //close if type is blocked and has 'closeAnyway' flag
        }
        //common logic
    }
    //other types
}

我不能写break:

'when'语句中不允许'break'和'continue'.考虑使用标签从外循环继续/中断.

这是一种return/break来自when陈述的方式吗？或者解决它的最佳方法是什么？

Answer 1

你可以用run与在标签的回报:

when(transaction.state) {
    Transaction.Type.EXPIRED,
    //about 10 more types
    Transaction.Type.BLOCKED -> run {
        if (transaction.type == Transaction.Type.BLOCKED && transaction.closeAnyway) {
            close(transaction)
            return@run //close if type is blocked and has 'closeAnyway' flag
        }
        //common logic
    }
    //other types
}

Answer 2

您可以使用标签来中断/继续/返回。例如：

transactions@ for (transaction in transactions) {
    when (transaction.state) {
        Transaction.Type.EXPIRED,
        Transaction.Type.BLOCKED -> {
            break@transactions
        }
    }
}

有关更多详细信息，请参见返回和跳转-Kotlin编程语言。