determining underlying numeric pointer type with reflect

[Davis Ford]

I need to determine if something is of type pointer to int, *int, which happens to be a field of a struct.

I'm trying to figure out the best way -- wondering if someone has a quick suggestion.

given a Value type: 

var whatIsIt interface{} // passed in


type := reflect.TypeOf(whatIsIt)


for i := 0; i < typ.NumField(); i++ {
  f := typ.Field(i)


  if f.Type.Kind() == reflect.Ptr {
     var num int
     if f.Type.AssignableTo(reflect.ValueOf(&num).Type()) {

        fmt.Println("it is a pointer to int")
     }
  }
}

This seems a bit obtuse -- but I welcome any better suggestions. 

[Ian Lance Taylor]

Would it work to simply write f.Type.Elem().Kind() == reflect.Int ?

Ian

[Davis Ford]

Seems like that would work, plugging it in.  Is there any issue calling Type.Elem().Kind() if the pointer is nil?

[Ian Lance Taylor]

On Fri, Oct 2, 2015 at 2:43 PM, Davis Ford <davi...@gmail.com> wrote:
> Seems like that would work, plugging it in. Is there any issue calling
> Type.Elem().Kind() if the pointer is nil?

No, Type.Elem() only refers to the type, not the value. Even if the
value of a *int is nil, the type *int still has an element, which is
the type int.

Ian

[Davis Ford]

Cool, thanks Ian!

[Matt Harden]

Do note that Type.Elem() will panic if the type's Kind is not Array, Chan, Map, Ptr, or Slice. If you have the original interface, why not just do `_, ok := whatIsIt.(*int)` ?

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[Matt Harden]

Oh, sorry ignore my email. I misunderstood the question.