I am working with an API that sends JSON data. The problem is that an array of a single element shows up as a single value. For example, consider the following JSON:
{ "names": ["Alice","Bob"] }
The API sends this as an array. But when the names field has a single element, the API sends this:
{ "names": "Alice" }
This is how I would normally decode this of response in Go:
type Response struct {
Names []string `json:"names"`
}
// later
d := &Response{}
_ = json.NewDecoder(resp).Decode(d) // resp would be a http.Response.Body containing the problematic JSON
Go decodes the first JSON correctly. However, after decoding the second JSON, the object contains an empty array.
I don't have any control over the API, so I have to get around this problem. How could I decode this JSON correctly in Go, so that the Names slice contains a single element? Thank you for your help.
You could implement the json.Unmarshaler interface and have it check the 0th raw byte for [ or " to find out whether it's an array or a string respectivelly:
type StringSlice []string
func (ss *StringSlice) UnmarshalJSON(data []byte) error {
if data[0] == '[' {
return json.Unmarshal(data, (*[]string)(ss))
} else if data[0] == '"' {
var s string
if err := json.Unmarshal(data, &s); err != nil {
return err
}
*ss = append(*ss, s)
}
return nil
}