如何创建 Kotlin DSL DSL 语法 Kotlin

Kotlin DSLs

Kotlin非常适合写你自己的Domain Specific Languages，也叫type-safe builders.正如你提到的，Anko库就是一个使用DSL的例子.在这里，你需要了解的最重要的语言特性是"Function Literals with Receiver"，你已经使用了它:Test.() -> Unit

Function Literals with Receiver - Basics

Kotlin支持"带接收者的函数文本"的概念.这允许在函数体without any specific qualifiers中的函数文本的receiver上调用可见方法.这是非常简单的similar to extension functions，在其中还可以访问扩展中的接收方对象的成员.

A simple example, also one of the coolest functions in the Kotlin standard library, isapply:

public inline fun <T> T.apply(block: T.() -> Unit): T { block(); return this }

正如您所看到的，这样一个带有receiver的函数literal在这里被当作参数block.这block被简单地执行，并且接收器(T的实例)被返回.在实际操作中，如下所示:

val text: String = StringBuilder("Hello ").apply {
            append("Kotliner")
            append("! ")
            append("How are you doing?")
        }.toString()

使用StringBuilder作为接收器，并在其上调用apply.block在{}(lambda表达式)中作为参数传递，不需要使用额外的限定符，只需多次调用append，这是一个StringBuilder的可视方法.

DSL中带接收器的函数文本

If you look at this example, taken from the documentation, you see this in action:

class HTML {
    fun body() { ... }
}

fun html(init: HTML.() -> Unit): HTML {
    val html = HTML()  // create the receiver object
    html.init()        // pass the receiver object to the lambda
    return html
}


html {       // lambda with receiver begins here
    body()   // calling a method on the receiver object
}

The html() function expects such a function literal with receiver with HTML as the receiver. In the function body you can see how it is used: an instance of HTML is created and the init is called on it.

Benefit

The caller of such an higher-order function expecting a function literal with receiver (like html()) you can use any visible HTML function and property without additional qualifiers (like this e.g.), as you can see in the call:

html {       // lambda with receiver begins here
    body()   // calling a method on the receiver object
}

你的例子

我创建了一个简单的例子来说明你想要什么:

class Context {
    fun onSuccess(function: OnSuccessAction.() -> Unit) {
        OnSuccessAction().function();
    }

    class OnSuccessAction {
        fun toast(s: String) {
            println("I'm successful <3: $s")
        }
    }
}

fun temp(function: Context.() -> Unit) {
    Context().function()
}

fun main(args: Array<String>) {
    temp {
        onSuccess {
            toast("Hello")
        }
    }
}