kotlin - Kotlin 中的密封数据类

Question

我有以下密封类

sealed class DownloadWallpaper : Result() {
    data class Progress(val hd: Boolean = false, ...) : DownloadWallpaper() 
    data class Success(val hd: Boolean = false, ...) : DownloadWallpaper()
    data class Error(val hd: Boolean = false, ...) : DownloadWallpaper()
}

我正在尝试执行以下操作。

//obs is of type Observable<Detail.Result.DownloadWallpaper> 
obs.map{ it.copy(hd = true) }

但我不能，有两个原因，因为 DownloadWallpaper 不是数据类。没有 .copy() 方法。如何告诉 Kotlin 这个密封类中的所有类实际上都是数据类？

其次，DownloadWallpaper 它本身没有“hd”字段。我可以使用 when 如何优雅地解决这个问题？ 这个解决方案很丑:

when (it) {
           is Detail.Result.DownloadWallpaper.Success -> it.copy(hd = true)
           is Detail.Result.DownloadWallpaper.Progress -> it.copy(hd = true)
           is Detail.Result.DownloadWallpaper.Error -> it.copy(hd = true)
 }

Answer 1

通过向您的密封类添加一些抽象方法，我能够访问复制方法而无需显式类型检查。自己看:

sealed class DownloadWallpaper {
    abstract val hd: Boolean
    abstract fun copy(hd: Boolean): DownloadWallpaper
}

data class Progress(override val hd: Boolean = false, val a: Any) : DownloadWallpaper() {
    override fun copy(hd: Boolean) = copy(hd = hd, a = a)
}
data class Success(override val hd: Boolean = false, val s: String) : DownloadWallpaper() {
    override fun copy(hd: Boolean) = copy(hd = hd, s = s)
}
data class Error(override val hd: Boolean = false, val c: Int) : DownloadWallpaper() {
    override fun copy(hd: Boolean) = copy(hd = hd, c = c)
}

fun main() {
    val dw: DownloadWallpaper = Progress()
    val newDw = dw.copy(hd = false)
    val newDwSameHd = dw.copy(hd = dw.hd)
}