how to use reflect.TypeOf([]string{“a”}).Elem()?

Question

I'm really new to golang and I'm struggling with the basics. I wrote a piece of code like this:

package main
import (
  "log"
  "reflect"
)

if reflect.TypeOf([]string{"a"}).Elem() == reflect.String {
  log.Println("success")
}
if reflect.TypeOf([]int{1}).Elem() == reflect.Int{
  log.Println("success")
}
if reflect.TypeOf([]float64{1.00}).Elem() == reflect.Float64 {
  log.Println("success")
}

When I run this code, I get the error

invalid operation: reflect.TypeOf([]string literal).Elem() == reflect.String (mismatched types reflect.Type and reflect.Kind)

I don't understand the documentation https://golang.org/pkg/reflect/ because I can't find examples of how to reference the different "types" or "kinds"

How should I be writing my if statements to do the comparisons I'm attempting?

Answer 1

reflect.Type is an interface with a method called Kind() . As per document:

    // Kind returns the specific kind of this type.
    Kind() Kind

So you should write :

if reflect.TypeOf([]string{"a"}).Elem().Kind() == reflect.String {
  log.Println("success")
}

Answer 2

To compare types, use:

if reflect.TypeOf([]string{"a"}).Elem() == reflect.TypeOf("") {
  log.Println("success")
}

To compare kinds, use:

if reflect.TypeOf([]string{"a"}).Elem().Kind() == reflect.String {
  log.Println("success")
}

If you want to test for a specific type, then compare types. If you want to determine what sort of type it is, then compare kinds.

This example might help:

type x string

The x and string types are both kinds of string. The kind comparison returns true for both:

fmt.Println(reflect.TypeOf(x("")).Kind() == reflect.String) // prints true
fmt.Println(reflect.TypeOf("").Kind() == reflect.String) // prints true

The x and string types are distinct:

fmt.Println(reflect.TypeOf(x("")) == reflect.TypeOf(""))    // prints false

Answer 3

For simple type comparisons like what you're showing, you don't need reflection. You can use a type assertion instead:

stuff := []interface{}{"hello", 1, nil}
for _, obj := range stuff {
        if _, ok := obj.(string); ok {
                fmt.Printf("is a string\n")
        } else if _, ok := obj.(int); ok {
                fmt.Printf("is an int\n")
        } else {
                fmt.Printf("is something else\n")
        }
}