Kotlin-限制扩展方法范围 [英] Kotlin - Restrict extension method scope

问题描述

有没有办法限制DSL中的扩展方法?

Is there a way to restrict extension methods in DSLs?

说我有一个这样的类结构:

Say I have a class structure like this:

class Outer {
    fun middle(op: Middle.() -> Unit): Middle {
        val middle = Middle()
        middle.op()
        return middle
    }
}

class Middle {
    fun inner(op: Inner.() -> Unit): Inner {
        val inner = Inner()
        inner.op()
        return inner
    }
}

class Inner

fun outer(op: Outer.() -> Unit): Outer {
    val outer = Outer()
    outer.op()
    return outer
}

然后我可以像这样创建通话:

I can then create a call like so:

outer {
    middle {
        inner {
            middle { }  // Here is the problem
        }
    }
}

我的问题是标记为middle { }的调用令人困惑，因为当它看起来像是添加到Inner时，它会在Outer上添加Middle.

My problem is that the marked middle { } call is confusing, as it adds a Middle to the Outer when it looks like it is adding to the Inner.

有没有办法不允许middle { }呼叫?

Is there a way to not allow the middle { } call?

推荐答案

您可以对deprecated使用解决方法:

You can use a workaround with deprecated:

class Outer {
    fun middle(op: Middle.() -> Unit): Middle {...}

    @Deprecated("can not be used inside a Outer block", level = DeprecationLevel.ERROR)
    fun outer(op: Outer.() -> Unit): Outer = TODO()
}

class Middle {
    fun inner(op: Inner.() -> Unit): Inner {...}

    @Deprecated("can not be used inside a Middle block", level = DeprecationLevel.ERROR)
    fun middle(op: Middle.() -> Unit): Middle = TODO()
}

class Inner {
    @Deprecated("can not be used inside a Inner block", level = DeprecationLevel.ERROR)
    fun inner(op: Inner.() -> Unit): Inner = TODO()
}

现在，编译器将给您一个错误，并且IDE不会在完成时建议错误的功能:

Now the compiler will give you an error, and IDE will not suggest a wrong function in the completion:

outer {
    middle {
        inner {
            middle { }  // error
        }
    }
}

但是对于大型DSL，您实际上不应该这样做.最好以@KirillRakhman等待 https://youtrack.jetbrains.com/issue/KT-11551 建议.

编辑:在修正示例后，它变得更小了.对于一个类，只有一个虚拟函数，毕竟并没有那么多样板.

After I fixed my example, it became much smaller. With one dummy function for a class it is not that much of boilerplate after all.

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