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package defaults
import (
"encoding/json"
"errors"
"reflect"
"strconv"
"time"
)
var (
errInvalidType = errors.New("not a struct pointer")
)
const (
fieldName = "default"
)
// Set initializes members in a struct referenced by a pointer.
// Maps and slices are initialized by `make` and other primitive types are set with default values.
// `ptr` should be a struct pointer
func Set(ptr interface{}) error {
if reflect.TypeOf(ptr).Kind() != reflect.Ptr {
return errInvalidType
}
v := reflect.ValueOf(ptr).Elem()
t := v.Type()
if t.Kind() != reflect.Struct {
return errInvalidType
}
for i := 0; i < t.NumField(); i++ {
if defaultVal := t.Field(i).Tag.Get(fieldName); defaultVal != "-" {
if err := setField(v.Field(i), defaultVal); err != nil {
return err
}
}
}
callSetter(ptr)
return nil
}
// MustSet function is a wrapper of Set function
// It will call Set and panic if err not equals nil.
func MustSet(ptr interface{}) {
if err := Set(ptr); err != nil {
panic(err)
}
}
func setField(field reflect.Value, defaultVal string) error {
if !field.CanSet() {
return nil
}
if !shouldInitializeField(field, defaultVal) {
return nil
}
isInitial := isInitialValue(field)
if isInitial {
switch field.Kind() {
case reflect.Bool:
if val, err := strconv.ParseBool(defaultVal); err == nil {
field.Set(reflect.ValueOf(val).Convert(field.Type()))
}
case reflect.Int:
if val, err := strconv.ParseInt(defaultVal, 0, strconv.IntSize); err == nil {
field.Set(reflect.ValueOf(int(val)).Convert(field.Type()))
}
case reflect.Int8:
if val, err := strconv.ParseInt(defaultVal, 0, 8); err == nil {
field.Set(reflect.ValueOf(int8(val)).Convert(field.Type()))
}
case reflect.Int16:
if val, err := strconv.ParseInt(defaultVal, 0, 16); err == nil {
field.Set(reflect.ValueOf(int16(val)).Convert(field.Type()))
}
case reflect.Int32:
if val, err := strconv.ParseInt(defaultVal, 0, 32); err == nil {
field.Set(reflect.ValueOf(int32(val)).Convert(field.Type()))
}
case reflect.Int64:
if val, err := time.ParseDuration(defaultVal); err == nil {
field.Set(reflect.ValueOf(val).Convert(field.Type()))
} else if val, err := strconv.ParseInt(defaultVal, 0, 64); err == nil {
field.Set(reflect.ValueOf(val).Convert(field.Type()))
}
case reflect.Uint:
if val, err := strconv.ParseUint(defaultVal, 0, strconv.IntSize); err == nil {
field.Set(reflect.ValueOf(uint(val)).Convert(field.Type()))
}
case reflect.Uint8:
if val, err := strconv.ParseUint(defaultVal, 0, 8); err == nil {
field.Set(reflect.ValueOf(uint8(val)).Convert(field.Type()))
}
case reflect.Uint16:
if val, err := strconv.ParseUint(defaultVal, 0, 16); err == nil {
field.Set(reflect.ValueOf(uint16(val)).Convert(field.Type()))
}
case reflect.Uint32:
if val, err := strconv.ParseUint(defaultVal, 0, 32); err == nil {
field.Set(reflect.ValueOf(uint32(val)).Convert(field.Type()))
}
case reflect.Uint64:
if val, err := strconv.ParseUint(defaultVal, 0, 64); err == nil {
field.Set(reflect.ValueOf(val).Convert(field.Type()))
}
case reflect.Uintptr:
if val, err := strconv.ParseUint(defaultVal, 0, strconv.IntSize); err == nil {
field.Set(reflect.ValueOf(uintptr(val)).Convert(field.Type()))
}
case reflect.Float32:
if val, err := strconv.ParseFloat(defaultVal, 32); err == nil {
field.Set(reflect.ValueOf(float32(val)).Convert(field.Type()))
}
case reflect.Float64:
if val, err := strconv.ParseFloat(defaultVal, 64); err == nil {
field.Set(reflect.ValueOf(val).Convert(field.Type()))
}
case reflect.String:
field.Set(reflect.ValueOf(defaultVal).Convert(field.Type()))
case reflect.Slice:
ref := reflect.New(field.Type())
ref.Elem().Set(reflect.MakeSlice(field.Type(), 0, 0))
if defaultVal != "" && defaultVal != "[]" {
if err := json.Unmarshal([]byte(defaultVal), ref.Interface()); err != nil {
return err
}
}
field.Set(ref.Elem().Convert(field.Type()))
case reflect.Map:
ref := reflect.New(field.Type())
ref.Elem().Set(reflect.MakeMap(field.Type()))
if defaultVal != "" && defaultVal != "{}" {
if err := json.Unmarshal([]byte(defaultVal), ref.Interface()); err != nil {
return err
}
}
field.Set(ref.Elem().Convert(field.Type()))
case reflect.Struct:
if defaultVal != "" && defaultVal != "{}" {
if err := json.Unmarshal([]byte(defaultVal), field.Addr().Interface()); err != nil {
return err
}
}
case reflect.Ptr:
field.Set(reflect.New(field.Type().Elem()))
}
}
switch field.Kind() {
case reflect.Ptr:
if isInitial || field.Elem().Kind() == reflect.Struct {
setField(field.Elem(), defaultVal)
callSetter(field.Interface())
}
case reflect.Struct:
if err := Set(field.Addr().Interface()); err != nil {
return err
}
case reflect.Slice:
for j := 0; j < field.Len(); j++ {
if err := setField(field.Index(j), defaultVal); err != nil {
return err
}
}
case reflect.Map:
for _, e := range field.MapKeys() {
var v = field.MapIndex(e)
switch v.Kind() {
case reflect.Ptr:
switch v.Elem().Kind() {
case reflect.Struct, reflect.Slice, reflect.Map:
if err := setField(v.Elem(), ""); err != nil {
return err
}
}
case reflect.Struct, reflect.Slice, reflect.Map:
ref := reflect.New(v.Type())
ref.Elem().Set(v)
if err := setField(ref.Elem(), ""); err != nil {
return err
}
field.SetMapIndex(e, ref.Elem().Convert(v.Type()))
}
}
}
return nil
}
func isInitialValue(field reflect.Value) bool {
return reflect.DeepEqual(reflect.Zero(field.Type()).Interface(), field.Interface())
}
func shouldInitializeField(field reflect.Value, tag string) bool {
switch field.Kind() {
case reflect.Struct:
return true
case reflect.Ptr:
if !field.IsNil() && field.Elem().Kind() == reflect.Struct {
return true
}
case reflect.Slice:
return field.Len() > 0 || tag != ""
case reflect.Map:
return field.Len() > 0 || tag != ""
}
return tag != ""
}
// CanUpdate returns true when the given value is an initial value of its type
func CanUpdate(v interface{}) bool {
return isInitialValue(reflect.ValueOf(v))
}
|
