Parse nested json array from a file - json

Question

I have a json file sample.json containing a json array as follows:
[
{
"time": "2021-01-04T00:11:32.362Z",
"extra_data": {
"id": "123"
},
"info": "event123"
},
{
"time": "2021-01-05T00:11:32.362Z",
"extra_data": {
"id": "456"
},
"info": "event456"
},
{
"time": "2021-01-06T00:11:32.362Z",
"extra_data": {
"id": "789"
},
"info": "event789"
}
]
I am trying to unmarshal this json array so that for each json object (i.e. event), I can access the id and info values. This is what I have so far:
func main() {
file, err := ioutil.ReadFile("/Users/janedoe/Downloads/sample.json")
var events Event
json.Unmarshal([]byte(file), &events)
fmt.Println(reflect.TypeOf(events))
// Reading each value by its key for each event
fmt.Println("Event123_Time :", events.Timestamp,
"\nEvent123_ExtraData_Id :", events.ExtraData.Id,
"\nEvent123_Info :", events.Info)
}
type Event struct {
Time string `json:"time"`
ExtraData ExtraData `json:"extra_data"`
Info string `json:"info"`
}
type ExtraData struct {
Id string `json:"id"`
}
The output that I am getting is:
main.Event
Event123_Time :
Event123_ExtraData_Id :
Event123_Info :
I am not getting any values, implying that the marshalling is not happening as expected. How can I fix this?

Answer 1

Since your json is an array, I think you want:
var events []Event
not
var events Event
Here's a version with that change:
func main() {
file, err := ioutil.ReadFile("/Users/janedoe/Downloads/sample.json")
if err != nil {
panic(err)
}
var events []Event
if err := json.Unmarshal([]byte(file), &events); err != nil {
panic(err)
}
fmt.Println(reflect.TypeOf(events))
for i, event := range events {
// Reading each value by its key for each event
fmt.Println(i, "Event123_Time :", event.Time,
"\nEvent123_ExtraData_Id :", event.ExtraData.Id,
"\nEvent123_Info :", event.Info)
}
}
type Event struct {
Time string `json:"time"`
ExtraData ExtraData `json:"extra_data"`
Info string `json:"info"`
}
type ExtraData struct {
Id string `json:"id"`
}