I want to get a string that represents a json like this one:
{ "votes": { "option_A": "3" } }
and include a "count" key in it so it ends like this:
{ "votes": { "option_A": "3" }, "count": "1" }
This is why I planned to convert it to json so I could add the count and then
make it a string again. The problem is I don't know the structure of that
JSON, so I can't use json.Unmarshal(in, &myStruct)
because that struct
varies. How can I do this?
The issue I had is that sometimes I will need to get at a value that is deeply
nested. Normally you would need to do a type assertion at each level, so I went
ahead and just made a method that takes a map[string]interface{}
and a
string
key, and returns the resulting map[string]interface{}
.
The issue that cropped up for me was that at some depths you will encounter a Slice instead of Map. So I also added methods to return a Slice from Map, and Map from Slice. I didnt do one for Slice to Slice, but you could easily add that if needed. Here are the methods:
package main
type Slice []interface{}
type Map map[string]interface{}
func (m Map) M(s string) Map {
return m[s].(map[string]interface{})
}
func (m Map) A(s string) Slice {
return m[s].([]interface{})
}
func (a Slice) M(n int) Map {
return a[n].(map[string]interface{})
}
and example code:
package main
import (
"encoding/json"
"fmt"
"log"
"os"
)
func main() {
o, e := os.Open("a.json")
if e != nil {
log.Fatal(e)
}
in_m := Map{}
json.NewDecoder(o).Decode(&in_m)
out_m := in_m.
M("contents").
M("sectionListRenderer").
A("contents").
M(0).
M("musicShelfRenderer").
A("contents").
M(0).
M("musicResponsiveListItemRenderer").
M("navigationEndpoint").
M("browseEndpoint")
fmt.Println(out_m)
}
package main
import "encoding/json"
func main() {
in := []byte(`{ "votes": { "option_A": "3" } }`)
var raw map[string]interface{}
if err := json.Unmarshal(in, &raw); err != nil {
panic(err)
}
raw["count"] = 1
out, err := json.Marshal(raw)
if err != nil {
panic(err)
}
println(string(out))
}
Source: Stackoverflow.com