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2019-04-27 09:22
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Golang通过JSON标记获取结构的字段名称

I have a struct:

type Human struct {
    Head  string  `json:"a1"`
    Body  string  `json:"a2"`
    Leg   string  `json:"a3"`
}

How can I get the struct's field name by providing JSON tag name? Probably something like this:

fmt.Println(getFieldName("a1")) // "Head"
fmt.Println(getFieldName("a2")) // "Body"
fmt.Println(getFieldName("a99")) // ""

func getFieldName(tag string) (fieldname string) {
    /* ... */
}

How should I implement the getFieldName function? I read online, it seems I need to use the reflect package, hmmm... any helping hand? :)

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我有一个结构:

  type Human struct {\  n头字符串`json:“ a1”`
主体字符串`json:“ a2”`
腿部字符串`json:“ a3”`
} 
   
 
 <  p>如何通过提供JSON标签名称来获取结构的字段名称? 大概是这样的: 
 
 
  fmt.Println(getFieldName(“ a1”))//“ Head” 
fmt.Println(getFieldName(“ a2”))// // 正文“ 
fmt.Println(getFieldName(” a99“))//”“ 
 
func getFieldName(标签字符串)(字段名称字符串){
 / * ... * / 
} 
    
 
 

我应该如何实现 getFieldName 函数? 我在网上阅读,看来我需要使用 reflect 包,嗯……有什么帮助吗? :)

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1条回答 默认 最新

  • duanaoou4105 2019-04-30 13:53
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    You can use the reflect package to loop over a struct's fields and match against their tag values.

    func getFieldName(tag, key string, s interface{}) (fieldname string) {
        rt := reflect.TypeOf(s)
        if rt.Kind() != reflect.Struct {
            panic("bad type")
        }
        for i := 0; i < rt.NumField(); i++ {
            f := rt.Field(i)
            v := strings.Split(f.Tag.Get(key), ",")[0] // use split to ignore tag "options" like omitempty, etc.
            if v == tag {
                return f.Name
            }
        }
        return ""
    }
    

    https://play.golang.com/p/2zCC7pZKJTz


    Alternatively, as pointed out by @icza, you can build up a map and then use that for quicker lookups.

    //                         Human            json       a1     Head
    var fieldsByTag = make(map[reflect.Type]map[string]map[string]string)
    
    func buildFieldsByTagMap(key string, s interface{}) {
        rt := reflect.TypeOf(s)
        if rt.Kind() != reflect.Struct {
            panic("bad type")
        }
    
        if fieldsByTag[rt] == nil {
            fieldsByTag[rt] = make(map[string]map[string]string)
        }
        if fieldsByTag[rt][key] == nil {
            fieldsByTag[rt][key] = make(map[string]string)
        }
    
        for i := 0; i < rt.NumField(); i++ {
            f := rt.Field(i)
            v := strings.Split(f.Tag.Get(key), ",")[0] // use split to ignore tag "options"
            if v == "" || v == "-" {
                continue
            }
            fieldsByTag[rt][key][v] = f.Name
        }
    }
    

    https://play.golang.com/p/qlt_mWsXGju

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