Citing from JSON and Go:
Without knowing this data's structure, we can decode it into an interface{} value with Unmarshal:
b := []byte(`{
"k1" : "v1",
"k3" : 10,
result:["v4",12.3,{"k11" : "v11", "k22" : "v22"}]
}`)
var f interface{}
err := json.Unmarshal(b, &f)
At this point the Go value in f would be a map whose keys are strings and whose values are themselves stored as empty interface values:
f = map[string]interface{}{
"k1": "v1",
"k3": 10,
"result": []interface{}{
"v4",
12.3,
map[string]interface{}{
"k11":"v11",
"k22":"v22",
},
},
}
To access this data we can use a type assertion to access f
's underlying map[string]interface{}:
m := f.(map[string]interface{})
We can then iterate through the map with a range statement and use a type switch to access its values as their concrete types:
for k, v := range m {
switch vv := v.(type) {
case string:
fmt.Println(k, "is string", vv)
case int:
fmt.Println(k, "is int", vv)
case []interface{}:
fmt.Println(k, "is an array:")
for i, u := range vv {
fmt.Println(i, u)
}
default:
fmt.Println(k, "is of a type I don't know how to handle")
}
}
In this way you can work with unknown JSON data while still enjoying the benefits of type safety.
More information about Go and JSON can be found in the original article. I changed the code snippets slightly to be more similar to the JSON in the question.