mirai-console/net.mamoe.mirai.console.command/fold

fold

inline fun <R> CommandSender.fold( ifIsConsole: ConsoleCommandSender.() -> R, ifIsUser: UserCommandSender.() -> R, otherwise: CommandSender.() -> R = { error("CommandSender ${this::class.qualifiedName} is not supported") }): R

折叠 AbstractCommandSender 的可能性.

当 this 为 ConsoleCommandSender 时执行 ifIsConsole
当 this 为 UserCommandSender 时执行 ifIsUser
否则执行 otherwise

示例

// 当一个指令执行过程出错
val exception: Exception = ...

sender.fold(
    ifIsConsole = { // this: ConsoleCommandSender
        sendMessage(exception.stackTraceToString()) // 展示整个 stacktrace
    },
    ifIsUser = { // this: UserCommandSender
        sendMessage(exception.message.toString()) // 只展示 Exception.message
    }
)

Return

ifIsConsole, ifIsUser 或 otherwise 执行结果.