如何在golang中获取 struct 的json字段名称

发布于11月29日

What is the way to get the json field names of this struct ?

type example struct {
    Id          int `json:"id"`
    CreatedAt   string `json:"created_at"`
    Tag         string `json:"tag"`
    Text        string `json:"text"`
    AuthorId    int `json:"author_id"`
}

我try 使用此功能打印字段:

func (b example) PrintFields() {
    val := reflect.ValueOf(b)
    for i := 0; i < val.Type().NumField(); i++ {
        fmt.Println(val.Type().Field(i).Name)
    }
}

Of course I get :

Id
CreatedAt
Tag
Text
AuthorId

But I would like something like :

id
created_at
tag
text
author_id

推荐答案

您可以使用StructTag类型来获取标签.我链接的文档包含示例，请查找它们，但您的代码可能如下所示

func (b example) PrintFields() {
  val := reflect.ValueOf(b)
  for i := 0; i < val.Type().NumField(); i++ {
     fmt.Println(val.Type().Field(i).Tag.Get("json"))
  }
}

NOTE The json tag format supports more than just field names, such as omitempty or string, so if you need an approach that takes care of that too, further improvements to the PrintFields function should be made:

我们需要判断json标签是否为-(即json:"-")
we need to check if name exists and isolate it

比如:

func (b example) PrintFields() {
  val := reflect.ValueOf(b)
  for i := 0; i < val.Type().NumField(); i++ {
    t := val.Type().Field(i)
    fieldName := t.Name

    switch jsonTag := t.Tag.Get("json"); jsonTag {
    case "-":
    case "":
        fmt.Println(fieldName)
    default:
        parts := strings.Split(jsonTag, ",")
        name := parts[0]
        if name == "" {
            name = fieldName
        }
        fmt.Println(name)
    }
  }
}