perelin perelin - 1 month ago 14
JSON Question

Parse JS array in JSON string as Golang map

An API I query returns a JSON where one of the elements should be an array but is wrapped in quotation marks. It seems therefore the "encoding/json" package doesn´t recognize that element as an array.

When I try to make that element accessible as a map I get the error:

interface conversion: interface is string, not []interface {}


Playground: https://play.golang.org/p/K1H01q-Dqc

package main

import (
"fmt"
"encoding/json"
)

func check(e error) {
if e != nil {
panic(e)
}
}

var incomingJson string = `{
"status":"success",
"content":"[{\"id\":\"567670128\"},{\"id\":\"567670129\"}]"
}`

func main() {

// Decode incoming json
var encodedJson map[string]interface{}
err := json.Unmarshal([]byte(incomingJson), &encodedJson)
check(err)
fmt.Println(encodedJson)

// Accessing "content" data
contentOjects := encodedJson["content"].([]interface{})
contentObject0 := contentOjects[0].(map[string]string)
fmt.Println(contentObject0)
}


How should I convert/cast the string in
["content"]
so I can parse it into
map[string]string
?

Answer

The value of "content" is a JSON string which by the way is another JSON encoded text. So if this is what you get, you may unmarshal the value of "content" just like you unmarshal any other JSON text:

var contentOjects []interface{}
err = json.Unmarshal([]byte(encodedJson["content"].(string)), &contentOjects)
check(err)
contentObject0 := contentOjects[0].(map[string]interface{})
fmt.Println(contentObject0)

Output:

map[id:567670128]

Alternatively you may unmarshal right into a value of type []map[string]interface{} (or even []map[string]string if you know it only contains string values):

// Accessing "content" data
var contentOjects2 []map[string]interface{}
err = json.Unmarshal([]byte(encodedJson["content"].(string)), &contentOjects2)
check(err)
fmt.Println(contentOjects2[0])

Output is the same:

map[id:567670128]

Try these on the Go Playground.

Comments