Use Array as function call arguments

Question

In JavaScript, you can use .apply to call a function and pass in an array/slice to use as function arguments.

function SomeFunc(one, two, three) {}

SomeFunc.apply(this, [1,2,3])

I'm wondering if there's an equivalent in Go?

func SomeFunc(one, two, three int) {}

SomeFunc.apply([]int{1, 2, 3})

The Go example is just to give you an idea.

Go is not a dynamic language and you shouldn't really need to do that kind of thing in Go. — fuz
– fuz, Commented Sep 14, 2014 at 8:27

AndrewN · Accepted Answer · 2014-09-14 15:16:44Z

2

They are called variadic functions and use the ... syntax, see Passing arguments to ... parameters in the language specification.

An example of it:

package main

import "fmt"

func sum(nums ...int) (total int) {
    for _, n := range nums { // don't care about the index
        total += n
    }
    return
}

func main() {
    many := []int{1,2,3,4,5,6,7}

    fmt.Printf("Sum: %v\n", sum(1, 2, 3)) // passing multiple arguments
    fmt.Printf("Sum: %v\n", sum(many...)) // arguments wrapped in a slice
}

Playground example

edited Sep 14, 2014 at 15:16

answered Sep 14, 2014 at 15:09

AndrewN

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1 Comment

daryl Over a year ago

Thanks for the answer. I actually found out about this a few hours later, surprised I hadn't tried it before. It seems obvious when you know.

OneOfOne · Accepted Answer · 2014-09-13 22:34:25Z

0

It is possible using reflection, specifically Value.Call, however you really should rethink why you want to do that, also look into interfaces.

fn := reflect.ValueOf(SomeFunc)
fn.Call([]reflect.Value{reflect.ValueOf(10), reflect.ValueOf(20), reflect.ValueOf(30)})

playground

answered Sep 13, 2014 at 22:34

OneOfOne

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4 Comments

daryl Over a year ago

What do you suggest with Interfaces?

OneOfOne Over a year ago

@daryl I meant you should think why you need to use this kind of dynamic calling and see if you can replace it with an interface.

Wessie Over a year ago

@OneOfOne this is the wrong solution, think thrice before you ever import reflect and especially when suggesting others to do so. See AndrewN's answer for the correct thing to do.

OneOfOne Over a year ago

@Wessie It's the right the solution for the question, it is the closest thing to function.apply in javascript, Andrew's solution would only work for one type.

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