gogjango/gjango

package structs

import "reflect"

// Merge receives two structs, and merges them excluding fields with tag name: `structs`, value "-"
func Merge(dst, src interface{}) {
    s := reflect.ValueOf(src)
    d := reflect.ValueOf(dst)
    if s.Kind() != reflect.Ptr || d.Kind() != reflect.Ptr {
        return
    }
    for i := 0; i < s.Elem().NumField(); i++ {
        v := s.Elem().Field(i)
        fieldName := s.Elem().Type().Field(i).Name
        skip := s.Elem().Type().Field(i).Tag.Get("structs")
        if skip == "-" {
            continue
        }
        if v.Kind() > reflect.Float64 &&
            v.Kind() != reflect.String &&
            v.Kind() != reflect.Struct &&
            v.Kind() != reflect.Ptr &&
            v.Kind() != reflect.Slice {
            continue
        }
        if v.Kind() == reflect.Ptr {
            // Field is pointer check if it's nil or set
            if !v.IsNil() {
                // Field is set assign it to dest

                if d.Elem().FieldByName(fieldName).Kind() == reflect.Ptr {
                    d.Elem().FieldByName(fieldName).Set(v)
                    continue
                }
                f := d.Elem().FieldByName(fieldName)
                if f.IsValid() {
                    f.Set(v.Elem())
                }
            }
            continue
        }
        d.Elem().FieldByName(fieldName).Set(v)
    }
}