在Kotlin中如何限制内部类的实例化只能在外部内部进行？

Question

有内在的

科特林拥有的:

class Outer {
    val insideCreatedInner: Inner = Inner()
    inner class Inner
}

val insideCreatedInner = Outer().insideCreatedInner // Should be visible and accessible
val outsideCreatedInner = Outer().Inner() // I want to disallow this

Java如何解决这个问题:

class Outer {
    Inner insideCreatedInner = new Inner();
    class Inner {
        private Inner() {}
    }
}

Outer.Inner insideCreatedInner = new Outer().insideCreatedInner;
Outer.Inner outsideCreatedInner = new Outer().new Inner(); // 'Inner()' has private access in 'Outer.Inner'

Answer 1

已编辑:要使< code>val字段可见，同时隐藏< code>Inner构造函数，使用可见的接口并使实现私有可能会很有用:

class Outer {
    val insideInner: Inner = InnerImpl()

    interface Inner {
        // ...
    }
    private inner class InnerImpl : Inner {
        // ...
    }
}


val outer = Outer()
val outsideInner = outer.InnerImpl() // Error! Cannot access '<init>': it is private in 'Inner'