kotlin 中使用的任何 function 類型

Question

我們可以很容易地定義一個 function，例如：

fun <T> f1(f2: KFunction<T>) {…}

然后這樣稱呼它：

fun f2() {...}
f1(::f2)

但是當我想這樣稱呼它時：

f1 {

}

它失敗了。 因為它需要 KFunction<TypeVariable>，但它實際上是 () -> Unit。

所以我這樣重寫它：

fun <K, T : Function<K>> f1(args: Array<Any> = arrayOf(), f2: T) {
    //f2.invoke(args)
    //it failed. I don't know how to call f2
}

f1 {…} //success

所以這就是問題所在。 我不知道如何調用任意匿名 function 類型

我試着這樣稱呼它：

inline fun <K, reified T : Function<K>> f1(args: Array<Any> = arrayOf(), f2: T) {
    val typeParams = args.map { it::class.java }.toTypedArray()
    T::class.java.getDeclaredMethod("invoke", *typeParams).invoke(f2, args) 
    // success. But I don't know if there is a bug
}

最后，我找到kotlin.reflect.jvm.Function.reflect()但是現在沒用了。 所以我想知道是否有更好的方法來做到這一點。

謝謝你的幫助。

Answer 1

這是我的最終解決方案。 它由生成器生成。 看起來很蠢，但是非常有用

@Suppress("UNCHECKED_CAST")
fun Function<*>.call(vararg args: Any?): Any? {
    return when(this) {
        is Function0 -> {
            invoke()
        }
        is Function1<*,*> -> {
            (this as Function1<Any?,Any?>).invoke(args[0])
        }
        is Function2<*,*,*> -> {
            (this as Function2<Any?,Any?,Any?>).invoke(args[0],args[1])
        }
        is Function3<*,*,*,*> -> {
            (this as Function3<Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2])
        }
        is Function4<*,*,*,*,*> -> {
            (this as Function4<Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3])
        }
        is Function5<*,*,*,*,*,*> -> {
            (this as Function5<Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4])
        }
        is Function6<*,*,*,*,*,*,*> -> {
            (this as Function6<Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5])
        }
        is Function7<*,*,*,*,*,*,*,*> -> {
            (this as Function7<Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5],args[6])
        }
        is Function8<*,*,*,*,*,*,*,*,*> -> {
            (this as Function8<Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5],args[6],args[7])
        }
        is Function9<*,*,*,*,*,*,*,*,*,*> -> {
            (this as Function9<Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5],args[6],args[7],args[8])
        }
        is Function10<*,*,*,*,*,*,*,*,*,*,*> -> {
            (this as Function10<Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5],args[6],args[7],args[8],args[9])
        }
        is Function11<*,*,*,*,*,*,*,*,*,*,*,*> -> {
            (this as Function11<Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5],args[6],args[7],args[8],args[9],args[10])
        }
        is Function12<*,*,*,*,*,*,*,*,*,*,*,*,*> -> {
            (this as Function12<Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5],args[6],args[7],args[8],args[9],args[10],args[11])
        }
        is Function13<*,*,*,*,*,*,*,*,*,*,*,*,*,*> -> {
            (this as Function13<Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5],args[6],args[7],args[8],args[9],args[10],args[11],args[12])
        }
        is Function14<*,*,*,*,*,*,*,*,*,*,*,*,*,*,*> -> {
            (this as Function14<Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5],args[6],args[7],args[8],args[9],args[10],args[11],args[12],args[13])
        }
        is Function15<*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*> -> {
            (this as Function15<Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5],args[6],args[7],args[8],args[9],args[10],args[11],args[12],args[13],args[14])
        }
        is Function16<*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*> -> {
            (this as Function16<Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5],args[6],args[7],args[8],args[9],args[10],args[11],args[12],args[13],args[14],args[15])
        }
        is Function17<*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*> -> {
            (this as Function17<Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5],args[6],args[7],args[8],args[9],args[10],args[11],args[12],args[13],args[14],args[15],args[16])
        }
        is Function18<*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*> -> {
            (this as Function18<Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5],args[6],args[7],args[8],args[9],args[10],args[11],args[12],args[13],args[14],args[15],args[16],args[17])
        }
        is Function19<*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*> -> {
            (this as Function19<Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5],args[6],args[7],args[8],args[9],args[10],args[11],args[12],args[13],args[14],args[15],args[16],args[17],args[18])
        }
        is Function20<*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*> -> {
            (this as Function20<Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5],args[6],args[7],args[8],args[9],args[10],args[11],args[12],args[13],args[14],args[15],args[16],args[17],args[18],args[19])
        }
        is Function21<*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*> -> {
            (this as Function21<Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5],args[6],args[7],args[8],args[9],args[10],args[11],args[12],args[13],args[14],args[15],args[16],args[17],args[18],args[19],args[20])
        }
        is Function22<*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*,*> -> {
            (this as Function22<Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?,Any?>).invoke(args[0],args[1],args[2],args[3],args[4],args[5],args[6],args[7],args[8],args[9],args[10],args[11],args[12],args[13],args[14],args[15],args[16],args[17],args[18],args[19],args[20],args[21])
        }
        is FunctionN<*> -> {
            (this as FunctionN<Any?>).invoke(*args)
        }

        else -> { throw RuntimeException() }
    }
}