class - 多参数构造函数的回调

Question

到目前为止，我尝试过的是使用单个参数的回调并且它有效:

class SomeClass (something:Int = 3, val callback: (Int) -> Unit) {
    fun doSomething() {
      callback(11)
    }
}

class AnotherClass {

    val something = SomeClass({onSomething(it)}) 

    protected fun onSomething(num: Int) {
        // ...
    }
}

但是如何使用多个参数来实现它，例如:

class SomeClass (something:Int = 3, val callback: (Int, String) -> Unit) {
    fun doSomething() {
      callback(11, "Yeah")
    }
}

class AnotherClass {

    val something = SomeClass(/* ...... what goes here???? */) 

    protected fun onSomething(num: Int, str: String) {
        // ...
    }
}

Answer 1

只需使用 lambda expression syntax带有显式参数:

val something = SomeClass { num, str -> onSomething(num, str) }

^{将 lambda 作为最后一个参数传递时，可以省略括号。}

此外，您可以使用 bound function reference当预期的和实际的函数签名完全匹配时:

val something = SomeClass(this::onSomething)