A bunch of reflective nonsense in go, but a good example

reflecty.go

package main

import (
	"fmt"
	"reflect"
)

type Example struct {
	A string
	B string
	C string
}

type AnotherExample struct {
	D string
	E string
	F string
}

func main() {
	ex := Example{C: "bar"}

	SetDefaults(&ex)
	fmt.Printf("%#v\n", ex)

	anex := AnotherExample{D: "bar", E: "foo"}
	SetDefaults(&anex)
	fmt.Printf("%#v\n", anex)

}

// Changes every empty string field to ".*"
func SetDefaults(ex interface{}) {
	v := reflect.ValueOf(ex).Elem()
	for i := 0; i < v.NumField(); i++ {
		f := v.Field(i)
		if s, ok := f.Interface().(string); ok && s == "" {
			f.Set(reflect.ValueOf(".*"))
		}
	}
}