Golang multiple json tag names for one field

Question

It it possible in Golang to use more than one name for a JSON struct tag ?

type Animation struct {
    Name    string  `json:"name"`
    Repeat  int     `json:"repeat"`
    Speed   uint    `json:"speed"`
    Pattern Pattern `json:"pattern",json:"frames"`
}

Voting to re-open. The question linked as duplicate with answer is for assigning multiple different name tags in a struct. The OP is asking for how to assign multiple json tags... which is a different question. — cheshirekow
– cheshirekow, Commented Dec 11, 2019 at 5:08
Dup, see good answers here: stackoverflow.com/questions/37118263/… — exyzzy
– exyzzy, Commented May 7, 2020 at 4:47

Zhang · Accepted Answer · 2018-07-09 10:59:50Z

20

you can use multiple json tag with third part json lib like github.com/json-iterator/go coding like below:

package main

import (
    "fmt"
    "github.com/json-iterator/go"
)

type TestJson struct {
    Name string `json:"name" newtag:"newname"`
    Age  int    `json:"age" newtag:"newage"`
}

func main() {

    var json = jsoniter.ConfigCompatibleWithStandardLibrary
    data := TestJson{}
    data.Name = "zhangsan"
    data.Age = 22
    byt, _ := json.Marshal(&data)
    fmt.Println(string(byt))

    var NewJson = jsoniter.Config{
        EscapeHTML:             true,
        SortMapKeys:            true,
        ValidateJsonRawMessage: true,
        TagKey:                 "newtag",
    }.Froze()

    byt, _ = NewJson.Marshal(&data)
    fmt.Println(string(byt))
}

output:

    {"name":"zhangsan","age":22}
    {"newname":"zhangsan","newage":22}

edited Jul 9, 2018 at 10:59

answered Jun 21, 2018 at 10:42

Zhang

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2 Comments

The 0bserver Over a year ago

Your solution answers for when somebody wants to add multiple different tags to different packages. ie in your case json and newtag. OP asked for a usecase when he/she wants to target the same package. ie. In json if you have to specify 2 different properties. Usecases for example in json formatting options, ORMs etc. Your solution is pretty much just working around that problem. no?

shubham rasal Over a year ago

Is there any pkg for yaml ?

TehSphinX · Accepted Answer · 2019-04-04 10:35:28Z

17

See How to define multiple name tags in a struct on how you can define multiple tags on one struct field.

You can also use a type Info map[string]interface{} instead of your struct.

Or you can use both types in your structure, and make method Details() which will return right pattern.

type Animation struct {
    Name    string  `json:"name"`
    Repeat  int     `json:"repeat"`
    Speed   uint    `json:"speed"`
    Pattern Pattern `json:"pattern"`
    Frame   Pattern `json:"frames"`
}

func (a Animation) Details() Pattern {
    if a.Pattern == nil {
        return a.Frame
    }
    return a.Pattern
}

edited Apr 4, 2019 at 10:35

TehSphinX

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answered Aug 6, 2016 at 22:24

Mayank Patel

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2 Comments

William Poussier Over a year ago

Thanks. I needed something like this for retro compatibility. This is good.

cheshirekow Over a year ago

I think this is a good answer, but IIUC you cannot use multiple json name tags to any useful effect. For example json:"pattern" json:"frames" will not tell Unmarshal to unmarshal either pattern or frames. So maybe it's worth noting after the link "but this doesn't work the way you want"

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