dongxuxian1123
2016-11-29 11:30
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如何在golang中获取结构的json字段名称?

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"`
}

I try to print the fields with this function :

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
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5条回答 默认 最新

  • dongpangfu6322 2016-11-29 11:40
    最佳回答

    You use the StructTag type to get the tags. The documentation I linked has examples, look them up, but your code could be something like

    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:

    1. we need to check whether the json tag is - (i.e. json:"-")
    2. we need to check if name exists and isolate it

    Something like this:

    func (b example) PrintFields() {
        val := reflect.ValueOf(b)
        for i := 0; i < val.Type().NumField(); i++ {
            t := val.Type().Field(i)
            fieldName := t.Name
    
            if jsonTag := t.Tag.Get("json"); jsonTag != "" && jsonTag != "-" {
                if commaIdx := strings.Index(jsonTag, ","); commaIdx > 0 {
                    fieldName = jsonTag[:commaIdx]
                }
            }
    
    
            fmt.Println(fieldName)
        }
    }
    
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