How to check interface is a map[string]string in golang

Question

I want to check the output variable is map[string]string or not. the output should be a map[string]string and it should be a ptr.

I checked ptr value. But I don't know how to check the key of map if is string or not.

sorry for my bad english

import (
    "fmt"
    "reflect"
)

func Decode(filename string, output interface{}) error {
    rv := reflect.ValueOf(output)
    if rv.Kind() != reflect.Ptr {
        return fmt.Errorf("Output should be a pointer of a map")
    }
    if rv.IsNil() {
        return fmt.Errorf("Output in NIL")
    }
    fmt.Println(reflect.TypeOf(output).Kind())
    return nil
}

Using [type switch](https://golang.org/ref/spec#Type_switches) or [type assertion](https://golang.org/ref/spec#Type_assertions). See this possible duplicate question+answer: [How to check if interface{} is a slice](http://stackoverflow.com/questions/40343471/how-to-check-if-interface-is-a-slice) — icza, Nov 02 '16 at 16:29
sure. So I know its a map ! how to check its map[string]string or map[string]int and etc... — ahmdrz, Nov 07 '16 at 08:45

score 26 · Accepted Answer · answered Nov 02 '16 at 16:30

You don't have to use reflect at all for this. A simple type assert will suffice;

unboxed, ok := output.(*map[string]string)
if !ok {
    return fmt.Errorf("Output should be a pointer of a map")
}
if unboxed == nil {
    return fmt.Errorf("Output in NIL")
}
// if I get here unboxed is a *map[string]string and is not nil

How to check interface is a map[string]string in golang

1 Answers1

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