struct not been entirely marshaled

Question

I have a struct what I need to marshal to consume the webservice, but in my tests I the Marshal function only encode one field:

type DataRows []struct {
    mData interface{}
}

type DataColumns []struct {
    mColumnName      string
    mColumnType      int
    mColumnPrecision int
    mColumnScale     int
}
type DataTables []struct {
    mDataColumns DataColumns
    mDataRows    DataRows
    mIndex       int
}

type CFFDataSet struct {
    mDataTables DataTables
    mUser       string
    DBServer    int
}

func main() {
    ds := CFFDataSet{
        mDataTables: DataTables{{
            mDataColumns: DataColumns{{
                mColumnName:      "Test",
                mColumnType:      1,
                mColumnPrecision: 1,
                mColumnScale:     1,
            }},
            mDataRows: DataRows{{
                mData: "Test",
            }},
            mIndex: 0,
        }},
        mUser:    "Teste",
        DBServer: 2,
    }

    marchaled, _ := json.Marshal(ds)
    fmt.Println(string(marchaled))
}

is returning

$ go run getrest.go
{"DBServer":2}

Can someone give me a hint why not this working ?

@JimB: Your choice of a duplicate was poor. It doesn't include an explanation of tags. — peterSO, Oct 16 '15 at 16:44
@peterSO: agree. This gets asked so frequently, I'm having trouble finding the good ones now — JimB, Oct 16 '15 at 16:45

evanmcdonnal · Accepted Answer · 2015-10-16T17:27:33.173

1

All your other fields are unexported (like private in other languages) and the unmarshaller can't access them. This is designated by the case of the first letter in the field name, needs to be uppercase.

For reference, here's an example using a field name on your struct that differs from the json's field name;

var jsonBlob = []byte(`[
    {"Name": "Platypus", "Purchase": "Monotremata"},
    {"Name": "Quoll",    "Purchase": "Dasyuromorphia"}
]`)
type Animal struct {
    Name  string
    Order string `json:"Purchase"`
}
var animals []Animal
err := json.Unmarshal(jsonBlob, &animals)
if err != nil {
    fmt.Println("error:", err)
}
fmt.Printf("%+v", animals)

https://play.golang.org/p/iJqaXQY7Ch

edited Oct 16 '15 at 17:27

answered Oct 16 '15 at 16:33

evanmcdonnal

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But the webservice what I need consume, the object starts with m lowercase. How can I consume him ? – Pedo Souza Oct 16 '15 at 16:38
I just replace m lower to upper and worked fine. Thanks a lot – Pedo Souza Oct 16 '15 at 16:48
1

@PedoSouza the other way to work with that is to use json annotations like `json:"mTheActualNameCouldBeAnything"` – evanmcdonnal Oct 16 '15 at 17:13
2

@evanmcdonnal: In Go, they are called JSON (struct field) tags, not annotations. – peterSO Oct 16 '15 at 17:30

struct not been entirely marshaled

1 Answers1