解组映射结构

Question

First of all I have one structure:

type times map[time.Time]struct{}

I need to write for it Marshal/Unmarshal methods for json converting. I've wrote MarshalJSON method, but do not understand how to write UnmarshalJSON method.

func (ts times) keys() []time.Time {
    res := make([]time.Time, 0, len(ts))
    for key := range ts {
        res = append(res, key)
    }
    return res
}

func (ts times) MarshalJSON() ([]byte, error) {
    return json.Marshal(ts.keys())
}

func (ts *times) UnmarshalJSON(b []byte) (error) {
    // ????
}  

Any idea?

Answer 1

You can decode json with the same way as you encoded(by taking only keys):

func (ts *times) UnmarshalJSON(b []byte) error {
    var t []time.Time

    err := json.Unmarshal(b, &t)
    if err != nil {
        return err
    }

    for _, v := range t {
        (*ts)[v] = struct{}{}
    }

    return nil
}

See: https://play.golang.org/p/0ViEBX_5iLw

But, I highly recommend to use a slice type, not a map. The decoded output is an array, so the type should also be an array too.