fields/fields.go

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/*
* Copyright (c) 2020 Alex aka mailoman <alex@webz.asia>
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* @author Alex aka mailoman <alex@webz.asia>
* @copyright Copyright (c) 2020 Alex aka mailoman <alex@webz.asia>
* @since 14.01.2020
*
*/
package fields
import (
"log"
"reflect"
"strings"
)
//Convert copies field values from one struct to another based on tags setup
func Сonvert(from interface{}, kind string, to interface{}) {
if nil == from {
log.Print("nil value is not supported")
return
}
v := reflect.ValueOf(from)
vt := reflect.ValueOf(to)
t := v.Type()
if t.Kind() != reflect.Struct {
log.Printf("type %s is not supported", t.Kind())
return
}
if vt.Kind() == reflect.Ptr {
vt = reflect.ValueOf(to).Elem()
}
for i := 0; i < t.NumField(); i++ {
f := t.Field(i)
// skip unexported fields. from godoc:
// PkgPath is the package path that qualifies a lower case (unexported)
// field name. It is empty for upper case (exported) field names.
if f.PkgPath != "" {
continue
}
fv := v.Field(i)
found, omit, omitempty := readTag(f, kind)
// skip if tag "omit" set.
if omit {
continue
}
// skip empty values when "omitempty" set.
if omitempty && fv.String() == "" {
continue
}
if found {
ft := vt.FieldByName(f.Name)
ft.Set(fv)
}
}
}
func readTag(f reflect.StructField, kind string) (bool, bool, bool) {
val, ok := f.Tag.Lookup(ConvertTagName())
if !ok {
return false, false, false
}
opts := strings.Split(val, ",")
return indexOf(opts, kind) > -1, indexOf(opts, OmitTagName()) > -1, indexOf(opts, OmitEmptyTagName()) > -1
}
func indexOf(a []string, x string) int {
for i, n := range a {
if x == n {
return i
}
}
return -1
}