仅当所有参数都不为null时，Kotlin调用函数 [英] Kotlin call function only if all arguments are not null

问题描述

如果所有(或某些)参数为null，kotlin中是否有一种方法可以防止函数调用?例如具有功能:

Is there a way in kotlin to prevent function call if all (or some) arguments are null? For example Having function:

fun test(a: Int, b: Int) { /* function body here */ }

在参数为null的情况下，我想防止进行空检查.例如，对于参数:

I would like to prevent null checks in case when arguments are null. For example, for arguments:

val a: Int? = null
val b: Int? = null 

我想替换:

a?.let { b?.let { test(a, b) } }

具有:

test(a, b)

我想函数定义语法可能看起来像这样:

I imagine that function definition syntax could look something like this:

fun test(@PreventNullCall a: Int, @PreventNullCall b: Int)

那等同于:

fun test(a: Int?, b: Int?) {
    if(a == null) {
        return
    }

    if(b == null) {
        return
    }

    // function body here
}

这样(或类似的东西)是否可以减少调用者(可能是函数作者)的冗余代码?

Is something like that (or similar) possible to reduce caller (and possibly function author) redundant code?

推荐答案

如果您不希望调用者自己进行这些检查，则可以在中介函数中执行空检查，然后在出现以下情况时调用真正的实现:他们通过了:

If you don't want callers to have to do these checks themselves, you could perform null checks in an intermediary function, and then call into the real implementation when they passed:

fun test(a: Int?, b: Int?) {
    a ?: return
    b ?: return
    realTest(a, b)
}

private fun realTest(a: Int, b: Int) {
    // use params
}

---

这是@Alexey Romanov在下面提出的功能的实现:

---

here's an implementation of the function @Alexey Romanov has proposed below:

inline fun <T1, T2, R> ifAllNonNull(p1: T1?, p2: T2?, function: (T1, T2) -> R): R? {
    p1 ?: return null
    p2 ?: return null
    return function(p1, p2)
}

fun test(a: Int, b: Int) {
    println("$a, $b")
}

val a: Int? = 10
val b: Int? = 5
ifAllNonNull(a, b, ::test)

如果需要其他功能，当然需要为2、3等参数实现ifAllNonNull功能.

Of course you'd need to implement the ifAllNonNull function for 2, 3, etc parameters if you have other functions where you need its functionality.

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