package main
import (
  "reflect"
)

// If you can verify fields without reflection, you should not use this!

// This can be useful when verifying JSON input from clients

// Pass in reference to object
// obj: struct to verify fields (pass reference with &)
// omitFields: map of field name to whether or not they should be omitted from the search
// fillEmpty: whether or not to fill empty fields with their zero value
// Returns whether or not all the fields (excluding omitFields) are non-nil

func VerifyFieldsExist(obj interface{}, omitFields map[string]bool, fillEmpty bool) bool {
	v := reflect.ValueOf(obj).Elem()
	for i := 0; i < v.NumField(); i++ {
		if v.Field(i).IsNil() {
			if !omitFields[v.Type().Field(i).Name] {
				return false
			} else if fillEmpty {
				v.Field(i).Set(reflect.New(v.Field(i).Type().Elem())) // zero the value if needed to fill empty
			}
		}
	}
	return true
}