CODEWITHSUNDEEP
jsongodecoder
Brian
Brian

Reputation: 7326

Go - JSON Decoder not initializing my struct

I am trying to decode some JSON retrieved via http.Get. However, when I check the structs I initialize with fmt.Println, they are always empty.

I suspect it is because my struct's structure does not agree with the returned JSON, but I am not sure how to fix it. In general, I am not exactly quite sure how the decoder works.

This is the JSON:

{
  "response":[
    {
      "list": {
        "category":"(noun)",
        "synonyms":"histrion|player|thespian|role player|performer|performing artist"
      }
    },
    {
      "list": {
        "category":"(noun)",
        "synonyms":"doer|worker|person|individual|someone|somebody|mortal|soul"
      }
    }
  ]
}

Here is what i have tried so far:

type SynonymResponse struct {
    lists []SynonymList
}

type SynonymList struct {
    category string
    synonyms string
}

var synonyms SynonymResponse;
dec := json.NewDecoder(response.Body)
err := dec.Decode(&synonyms)
if err != nil {
    log.Fatal(err)
}
fmt.Println(synonyms)

EDIT: Per @Leo's answer and @JimB's hint, there are two issues with my attempt. Below is the proper set of structs, though as Leo pointed out, this will be empty: 

type SynonymResponses struct {
    resp []SynonymResponse
}

type SynonymResponse struct {
    listo SynonymList
}

type SynonymList struct {
    cat string
    syns string
}

Upvotes: 1

Views: 144

Answers (1)

Leo Correa
Leo Correa

Reputation: 19839

In order for your JSON to be picked up by the decoder, the fields in your struct must be exported.

This means you need you capitalize the field names. If you have custom naming on your fields -> json conversion, you can add json tags to your structs.

This will fix your issue:

type SynonymResponse struct {
    Lists []SynonymList `json:"response"`
}

type SynonymList struct {
    Category string `json:"category"`
    Synonyms string `json:"synonyms"`
}

Upvotes: 6

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