Kotlin:可空的属性委托可观察

Question

在Kotlin中,我们可以为非null属性定义一个observable,

var name: String by Delegates.observable("<no name>") {
    prop, old, new ->
    println("$old -> $new")
}

但这是不可能的

var name: String? by Delegates.observable("<no name>") {
    prop, old, new ->
    println("$old -> $new")
}

为可空属性定义observable的方法是什么？

编辑:这是编译错误

Property delegate must have a 'setValue(DataEntryRepositoryImpl, KProperty<*>, String?)' method. None of the following functions is suitable: 
public abstract operator fun setValue(thisRef: Any?, property: KProperty<*>, value: String): Unit defined in kotlin.properties.ReadWriteProperty

Answer 1

由于某种原因,类型推断在这里失败了.您必须手动指定委托的类型.相反,您可以省略属性类型声明:

var name by Delegates.observable<String?>("<no name>") {
    prop, old, new ->
    println("$old -> $new")
}

请通过https://youtrack.jetbrains.com/issues/KT提交问题