Golang自定义结构体转map的操作

func newUser() User {
 name := "user"
 MyGithub := GithubPage{
 URL: "https://github.com/liangyaopei",
 Star: 1,
 }
 NoDive := StructNoDive{NoDive: 1}
 dateStr := "2020-07-21 12:00:00"
 date, _ := time.Parse(timeLayout, dateStr)
 profile := Profile{
 Experience: "my experience",
 Date:    date,
 }
 return User{
 Name:   name,
 Github:  MyGithub,
 NoDive:  NoDive,
 MyProfile: profile,
 }
}
 
type User struct {
 Name   string    `map:"name,omitempty"`    // string
 Github  GithubPage  `map:"github,dive,omitempty"` // struct dive
 NoDive  StructNoDive `map:"no_dive,omitempty"`   // no dive struct
 MyProfile Profile   `map:"my_profile,omitempty"` // struct implements its own method
}
 
type GithubPage struct {
 URL string `map:"url"`
 Star int  `map:"star"`
}
 
type StructNoDive struct {
 NoDive int
}
 
type Profile struct {
 Experience string  `map:"experience"`
 Date    time.Time `map:"time"`
}
 
// its own toMap method
func (p Profile) StructToMap() (key string, value interface{}) {
 return "time", p.Date.Format(timeLayout)
}

data, _ := json.Marshal(&user)
m := make(map[string]interface{})
json.Unmarshal(data, &m)

map[string]interface{}{
 "name":  "user",
 "no_dive": StructNoDive{NoDive: 1},
  // dive struct field
 "url":   "https://github.com/liangyaopei",
 "star":  1,
  // customized method
 "time":  "2020-07-21 12:00:00",
}

const (
 OptIgnore  = "-"
 OptOmitempty = "omitempty"
 OptDive   = "dive"
)
 
const (
 flagIgnore = 1 << iota
 flagOmiEmpty
 flagDive
)
 
func readTag(f reflect.StructField, tag string) (string, int) {
 val, ok := f.Tag.Lookup(tag)
 fieldTag := ""
 flag := 0
 
 // no tag, use field name
 if !ok {
 return f.Name, flag
 }
 opts := strings.Split(val, ",")
 
 fieldTag = opts[0]
 for i := 1; i < len(opts); i++ {
 switch opts[i] {
 case OptIgnore:
  flag |= flagIgnore
 case OptOmitempty:
  flag |= flagOmiEmpty
 case OptDive:
  flag |= flagDive
 }
 }
 return fieldTag, flag
}

for i := 0; i < t.NumField(); i++ {
    ...
    switch fieldValue.Kind() {
 case reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int, reflect.Int64:
  res[tagVal] = fieldValue.Int()
 case reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint, reflect.Uint64:
  res[tagVal] = fieldValue.Uint()
 case reflect.Float32, reflect.Float64:
  res[tagVal] = fieldValue.Float()
 case reflect.String:
  res[tagVal] = fieldValue.String()
 case reflect.Bool:
  res[tagVal] = fieldValue.Bool()
 default:
 }
  }
}

for i := 0; i < t.NumField(); i++ {
 fieldType := t.Field(i)
 
 // ignore unexported field
 if fieldType.PkgPath != "" {
  continue
 }
 // read tag
 tagVal, flag := readTag(fieldType, tag)
 
 if flag&flagIgnore != 0 {
  continue
 }
 
 fieldValue := v.Field(i)
 if flag&flagOmiEmpty != 0 && fieldValue.IsZero() {
  continue
 }
 
 // ignore nil pointer in field
 if fieldValue.Kind() == reflect.Ptr && fieldValue.IsNil() {
  continue
 }
 if fieldValue.Kind() == reflect.Ptr {
  fieldValue = fieldValue.Elem()
 }
 
 // get kind
 switch fieldValue.Kind() {
 case reflect.Struct:
  _, ok := fieldValue.Type().MethodByName(methodName)
  if ok {
  key, value, err := callFunc(fieldValue, methodName)
  if err != nil {
   return nil, err
  }
  res[key] = value
  continue
  }
  // recursive
  deepRes, deepErr := StructToMap(fieldValue.Interface(), tag, methodName)
  if deepErr != nil {
  return nil, deepErr
  }
  if flag&flagDive != 0 {
  for k, v := range deepRes {
   res[k] = v
  }
  } else {
  res[tagVal] = deepRes
  }
 default:
 }
  }
  ...
}
 
// call function
func callFunc(fv reflect.Value, methodName string) (string, interface{}, error) {
 methodRes := fv.MethodByName(methodName).Call([]reflect.Value{})
 if len(methodRes) != methodResNum {
 return "", nil, fmt.Errorf("wrong method %s, should have 2 output: (string,interface{})", methodName)
 }
 if methodRes[0].Kind() != reflect.String {
 return "", nil, fmt.Errorf("wrong method %s, first output should be string", methodName)
 }
 key := methodRes[0].String()
 return key, methodRes[1], nil
}

switch fieldValue.Kind() {
 case reflect.Slice, reflect.Array:
  _, ok := fieldValue.Type().MethodByName(methodName)
  if ok {
  key, value, err := callFunc(fieldValue, methodName)
  if err != nil {
   return nil, err
  }
  res[key] = value
  continue
  }
      res[tagVal] = fieldValue
      ....
}

switch fieldValue.Kind() {
 ...
 case reflect.Map:
  res[tagVal] = fieldValue
 case reflect.Chan:
  res[tagVal] = fieldValue
 case reflect.Interface:
  res[tagVal] = fieldValue.Interface()
 default:
 }