Casting From a list of strings to a list of interface in go

Question

I want to pass in a list of strings as generic parameters in go, but not sure if its possible. I have workarounds but feel like I'm just not able to get syntax correct.

package main

import "fmt"

func Set(otherFields ...interface{}) {
  fmt.Printf("%v", otherFields)
}

func main() {
  a := []string {"Abc", "def", "ghi"}
  Set(a)  // incorrect behavior because a passed through as a list, rather than a bunch of parameters 
//   Set(a...)  // compiler error: cannot use a (type []string) as type []interface {} in argument to Set
//  Set([]interface{}(a)) // compiler error: cannot convert a (type []string) to type []interface {}
  // This works but I want to do what was above.
  b := []interface{} {"Abc", "def", "ghi"}
  Set(b...)
}

See the [FAQ](https://golang.org/doc/faq#convert_slice_of_interface). — Charlie Tumahai, Dec 11 '15 at 00:11

score 3 · Answer 1 · edited May 23 '17 at 11:59

You have to deal with each string individually. You can't just cast the whole collection. Here's an example;

package main

import "fmt"

func main() {
  a := []string {"Abc", "def", "ghi"}
  b := []interface{}{} // initialize a slice of type interface{}

  for _, s := range a {
     b = append(b, s) // append each item in a to b
  }
  fmt.Println(len(b)) // prove we got em all

  for _, s := range b {
    fmt.Println(s) // in case you're real skeptical
  }

}

https://play.golang.org/p/VWtRTm01ah

As you can see, no cast is necessary because the collection of type inferface{} will accept any type (all types implement the empty interface Go equivalent of a void pointer in C). But you do have to deal with each item in collection individually.

Casting From a list of strings to a list of interface in go

1 Answers1