doulangtiao4508 2018-10-09 13:41
浏览 56


In Golang, I have a struct whose member is a custom int type with constant values. Basically, the custom type is a logical enum.

type Flavor int

const (
    Vanilla Flavor = iota

func (f *Flavor) MarshalJSON() ([]byte, error) {
    return []byte(strconv.Quote(f.String())), nil

The custom type has defined MarshalJSON and UnmarshalJSON functions so when I serialize the custom type to JSON, I expect to get the string of the value in the serialized output, not the int value.

My issue is that if I have a pointer to a containing type, then the containing type marshals using the custom function but if try to marshal with just a struct value, the custom MarshalJSON is not invoked by the JSON package

type Dessert struct {
    Flavor Flavor `json:"flavor"`
    Count  int
    d := Dessert{Strawberry, 13}

    b, err = json.Marshal(d) // !! does not invoke members Marshal !!
    b, err = json.Marshal(&d) // works as expected



I expected the second output in both case.
Why does passing a struct value not invoke MarshalJSON on the member but it does encode otherwise correct JSON?

see for full working code

  • 写回答

2条回答 默认 最新

  • 普通网友 2018-10-09 14:00

    In your code Flavor does not have a method MarshalJSON as you defined the method for *Flavor only.

    If you want type Flavor to have the MarshalJSON method you must define it on Flavor not *Flavor.

    本回答被题主选为最佳回答 , 对您是否有帮助呢?



  • ¥20 keepalive配置业务服务双机单活的方法。业务服务一定是要双机单活的方式
  • ¥50 关于多次提交POST数据后,无法获取到POST数据参数的问题
  • ¥15 win10,这种情况怎么办
  • ¥15 如何在配置使用Prettier的VSCode中通过Better Align插件来对齐等式?(相关搜索:格式化)
  • ¥100 在连接内网VPN时,如何同时保持互联网连接
  • ¥15 MATLAB中使用parfor,矩阵Removal的有效索引在parfor循环中受限制
  • ¥20 Win 10 LTSC 1809版本如何无损提升到20H1版本
  • ¥50 win10 LTSC 虚拟键盘不弹出
  • ¥15 寻找能匹配的液晶显示屏。
  • ¥30 微信小程序请求失败,网页能正常带锁访问