Passing pointer to string array in Golang

Question

I am trying to pass string array to the function, print values, modify it and then as the function is finished print value of the string array.

Here is my sample code which does not work but present what i want to achive:

package main
import (
    "fmt"
)
func SendData(a *[]string) {
    fmt.Println(*a)
    *a = *a[:0]
}
func main() {
    var s []string
    s = append(s, "dat","boi")
    SendData(&s)
    fmt.Println(s)
}

This is the error at compilation: cannot slice a (type *[]string)

You can slice a pointer to an array directly, you have a pointer to a slice. Just add parens: `(*a)[:0]` — JimB, Sep 05 '17 at 21:52
Hah, I typo'd my test and jumped straight to a two line answer. Silly me — RayfenWindspear, Sep 05 '17 at 21:55
@JimB Did you meant *a =(*a)[:0] ? It doesn't work for me. :s — Mac, Sep 05 '17 at 22:00
@Mac: what do you expect to happen? https://play.golang.org/p/wBDVivZNAw — JimB, Sep 05 '17 at 22:02
@Mac Are you getting an error or just not getting your expected result? Because It's working for us. — Topo, Sep 05 '17 at 22:18
It worked in example given by JimB. Maybe I kept compiling old code by mistake on my machine. — Mac, Sep 06 '17 at 06:23

score 3 · Accepted Answer · answered Sep 05 '17 at 21:54

To fix the error, just change *a[:0] to (*a)[:0] to get the object the pointer is pointing to, and then slice that object, instead of trying to slice the pointer.

The next is just my opinion:

However you don't need the * on the parameter, slices contain a pointer to the underlying array, so a copy of the slice points to the same array. And if you are going to assign another thing to the slice variable I recommend returning the new slice, like this:

package main
import (
    "fmt"
)
func SendData(a []string) []string {
    fmt.Println(a)
    a = a[:0]
    return a
}
func main() {
    var s []string
    s = append(s, "dat","boi")
    s = SendData(s)
    fmt.Println(s)
}

*a = (*a)[:0] Doesn't really seem to work. – Mac Sep 05 '17 at 22:02 — Mac, Sep 05 '17 at 22:02

Passing pointer to string array in Golang

1 Answers1