Accessing values from postgres jsonb column in Golang-CodePudding

I am getting a jsonb column from postgres which has value something like

{
"a": 123,
"b": "some str",
"c": {"d": 23},
"e": {"f":34, "g", 434}
}

How can i access keys a, b, d, f, g? Thanks

EDIT: getting the jsonb column "vars":

type Msg struct{
    Id int
    Vars map[string]interface{}
}
queryToGetD := "select id, vars from msg_table"
if rows, errRow := db.Query(queryToGetD); errRow != nil {
    return nil, fmt.Errorf("error while getting data \nquery %s \nerror %s", queryToGetD, err)
} else {
    func (){
        defer rows.Close()
        for rows.Next(){
            var msg Msg
            var vars string
            if err := rows.Scan(&msg.Id, &vars); err != nil{
                // handle error
                continue
            }else{
                if err := json.Unmarshal([]byte(vars), &msg.Vars); err != nil {
                    // handle error
                    continue
                }
                // Add msg to the needed slice
            }
        }
    }
}

CodePudding user response：

For a and b you can do msg.Vars["a"] and msg.Vars["b"] respectively to access those values. For d, f, and g you need to first access their parents just like you would access a and b. Then you need to type-assert the result of that access to the map[string]interface{} type and then access the desired fields through the result of the type assertion.

fmt.Println(msg.Vars["a"]) // access a
fmt.Println(msg.Vars["b"]) // access b

c := msg.Vars["c"].(map[string]interface{}) // access c and type-assert as map[string]interface{}
fmt.Println(c["d"]) // then access d

https://go.dev/play/p/oZERUsL2EUY

Or use a struct that matches the json, then you can access the fields with the selector expression

type Vars struct {
    A int    `json:"a"`
    B string `json:"b"`
    C struct {
        D int `json:"d"`
    } `json:"c"`
    E struct {
        F int `json:"f"`
        G int `json:"g"`
    } `json:"e"`
}

// ...

fmt.Println(msg.Vars.A)
fmt.Println(msg.Vars.B)
fmt.Println(msg.Vars.C.D)
fmt.Println(msg.Vars.E.F)
fmt.Println(msg.Vars.E.G)

https://go.dev/play/p/6ur78SNB_bL