Parsing complex JSON with Go

Question

I'm having issues digesting some nested JSON with Go. My primary issue is that I can't model my struct correctly to try and get the library to pull any information in. Here is a sample of the JSON data: http://pastebin.com/fcGQqi5z

The data is from a bank and has been scrubbed for privacy. Ideally I'm only interested in the transactions ID, the amount, and the description. Is there a way to just pull these values with Go?

This was my initial attempt:

type Trans struct {
  TransId string
  Amount int
  Description string
}

can you post valid json please that can be easily copy/pasted? — OneOfOne
– OneOfOne, Commented Oct 3, 2014 at 14:41

OneOfOne · Accepted Answer · 2014-10-03 15:38:20Z

1

You were on the right tracks:

type Trans struct {
    TransId     string
    Amount      float64
    Description string
}

func main() {
    var data struct {
        Record []Trans
    }
    if err := json.Unmarshal([]byte(j), &data); err != nil {
        fmt.Println(err)
        return
    }
    fmt.Printf("%#v\n", data.Record)
}

playground

//edit

type Trans struct {
    TransId     string
    Amount      float64
    Description string
    RawInfo     []map[string]json.RawMessage `json:"AdditionalInfo"`
}

// also this assumes that 1. all data are strings and 2. they have unique keys
// if this isn't the case, you can use map[string][]string or something
func (t *Trans) AdditionalInfo() (m map[string]string) {
    m = make(map[string]string, len(t.RawInfo))
    for _, info := range t.RawInfo {
        for k, v := range info {
            m[k] = string(v)
        }
    }
    return
}

playground

edited Oct 3, 2014 at 15:38

answered Oct 3, 2014 at 14:52

OneOfOne

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3 Comments

Joshua Gilman Over a year ago

Since Amount and Description are nested in "AdditionalInfo" how does the parser know to grab it without explicitly telling it that they are located inside "AdditionalInfo" ?

Joshua Gilman Over a year ago

I stand corrected. Just for learning sake, how would I incorporate any details inside "AdditionalInfo"?

OneOfOne Over a year ago

@JoshuaGilman I updated the post, basically since AdditionalData has no real format, you can use []map[string]string or []map[string]json.RawMessage.

jmaloney · Accepted Answer · 2014-10-03 14:50:09Z

1

type Records struct {
    Records []Record `json:"record"`
}

type Record struct {
    TransId string
    Amount float64
    Description string
}

func main() {
    r := Records{}
    if err := json.Unmarshal([]byte(data), &r); err != nil {
        log.Fatal(err)
    }

    fmt.Println(r)
}

answered Oct 3, 2014 at 14:50

jmaloney

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