Golang: get the type of slice

Question

I am using reflect package to get the type of arbitrary array, but getting

   prog.go:17: cannot use sample_array1 (type []int) as type []interface {} in function argument [process exited with non-zero status]

How do I get the type from array? I know how to get it from value.

  func GetTypeArray(arr []interface{}) reflect.Type {
      return reflect.TypeOf(arr[0])
  }

http://play.golang.org/p/sNw8aL0a5f

Answer 1

Change:

GetTypeArray(arr []interface{})

to:

GetTypeArray(arr interface{})

By the way, []int is not an array but a slice of integers.

Answer 2

The fact that you're indexing the slice is unsafe - if it's empty, you'll get an index-out-of-range runtime panic. Regardless, it's unnecessary because of the reflect package's Elem() method:

type Type interface {

    ...

    // Elem returns a type's element type.
    // It panics if the type's Kind is not Array, Chan, Map, Ptr, or Slice.
    Elem() Type

    ...
}

So, here's what you want to use:

func GetTypeArray(arr interface{}) reflect.Type {
      return reflect.TypeOf(arr).Elem()
}

Note that, as per @tomwilde's change, the argument arr can be of absolutely any type, so there's nothing stopping you from passing GetTypeArray() a non-slice value at runtime and getting a panic.