mirai-core-api/net.mamoe.mirai.message.data/AbstractPolymorphicMessageKey

AbstractPolymorphicMessageKey

abstract class AbstractPolymorphicMessageKey<out B : SingleMessage, out M : B>(baseKey: MessageKey<B>, safeCast: (SingleMessage) -> M?) : AbstractMessageKey<M> , MessageKey<M>

多态 MessageKey.

示例: HummerMessage

                 MessageContent
                       ↑
                 HummerMessage
                       ↑
          +------------+-------------+------------+
          |            |             |            |
    PokeMessage     VipFace      FlashImage      ...

当连接一个 VipFace 到一个 MessageChain 时, 由于 VipFace 最上层为 MessageContent, 消息链中第一个 MessageContent 会被 (保留顺序地) 替换为 VipFace, 其他所有 MessageContent 都会被删除.

如:

val source: MessageSource = ...

val result = messageChainOf(PlainText("a"), PlainText("b"), source, AtAll) + VipFace.LiuLian
// result 为 [VipFace.LiuLian, source]

val result = source1 + source2
// result 为 [source2], 总是右侧替换左侧

Constructors

AbstractPolymorphicMessageKey

fun <out B : SingleMessage, out M : B> AbstractPolymorphicMessageKey(baseKey: MessageKey<B>, safeCast: (SingleMessage) -> M?)

Properties

safeCast

abstract val safeCast: (SingleMessage) -> M?

将一个 SingleMessage 强转为 M 类型. 在类型不符合时返回 null

Inheritors

Key