How to unmarshal JSON in Golang where the objects have string keys

Question

I have some JSON that looks like this:

{
  "ABC": {"symbol": "abc", "open": 42},
  "DEF": {"symbol": "abc", "open": 42},
  "GHI": {"symbol": "abc", "open": 42}
}

And I don't need the ABC/DEF/GHI part, only the part on the right. The values of ABC, DEF, and GHI are of type entity.Day in my code, which looks something like this:

type Day struct {
    Symbol           string    `json:"symbol"  sql:"symbol"`
    Date             time.Time `json:"date"  sql:"date"`
    OpenP            float64   `json:"open"  sql:"open"`
    HighP            float64   `json:"high"  sql:"high"`
    LowP             float64   `json:"low"  sql:"low"`
    CloseP           float64   `json:"close"  sql:"close"`
    VolumeP          float64   `json:"volume"  sql:"volume"`
    Label            string    `json:"label" sql:"-"`
    ChangeOverTime   float64   `json:"changeOverTime"  sql:"change_over_time"`
    UnadjustedVolume float64   `json:"unadjustedVolume"  sql:"unadjusted_volume"`
    Change           float64   `json:"change"  sql:"change"`
    ChangePercent    float64   `json:"changePercent"  sql:"change_percent"`
    VWAP             float64   `json:"vwap"  sql:"vwap"`
}

There are other endpoints that produce entity.Days, however this is the only one that's structured like this. How can I unmarshal the JSON into, ideally, an array of entity.Days?

My first thought was to make an intermediate data structure:

type previous struct {
    tckrs map[string]entity.Day
}

p := previous{tckrs: make(map[string]entity.Day)}
json.Unmarshal(res, &p)

That code produces an empty struct and json.Unmarshal returns a nil error. Can you help me?

PS - I searched around quite a bit and I found similar answers and lots of other people trying the map approach, although that did not work for me.

json.Unmarshal(res,&p.tckrs)?

leaf bebop
– leaf bebop

2018-07-12 03:24:37 +00:00
Commented Jul 12, 2018 at 3:24 — leaf bebop
– leaf bebop, Commented Jul 12, 2018 at 3:24

eugenioy · Accepted Answer · 2018-07-12 03:25:40Z

3

The type previous you defined would require your JSON to represent an object with one top level field containing the map.

Since your JSON models a map directly, you can use a map to unmarshal it.

Try just:

p := make(map[string]Day)
json.Unmarshal(res, &p)

answered Jul 12, 2018 at 3:25

eugenioy

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1 Comment

onwsk8r Over a year ago

Wow, duh.. I was hoping this question could help some other people as well; I guess it will if they miss something obvious like I did. Thank you for being really nice about it!

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