kotlin - Kotlin覆盖父类(super class)型变量

Question

考虑两类:

abstract class ParentRepository {}

class ChildRepository : ParentRepository {}

abstract class ParentClass {
    protected abstract var repository: ParentRepository
}

class ChildClass : ParentClass {
    override var repository: ChildRepository
}

最后一部分不起作用:

override var repository: ChildRepository

它会提示:

Type of 'repository' doesn't match the type of the overridden var-property 'protected abstract var repository: ParentRepository

我理解问题所在，但是我不明白为什么它不起作用– ChildRepository是ParentRepository的实例，这是我习惯于Java的常识。

Answer 1

您必须将repository声明为val。您仍然可以将其覆盖为var:

protected abstract val repository: ParentRepository

override var repository: ChildRepository