JSON解组后自动创建计算字段

Question

Simplified example

Lets say I have a struct which I use to unmarshall some json:

type DataEntry struct {
    FirstName string `json:"first"`
    LastName  string `json:"last"`
    FullName  string
}

What I want to fill the FullName property, which would be FirstName + LastName.

---

What I am currently doing is defining a method for DataEntry, which does these kind of computations:

func (de *DataEntry) Compute() {
   de.FullName = de.FirstName + " " + de.LastName
}

and calling if after the struct gets filled from the JSON:

// Grab data
request, _ := http.Get("http://........")
var entry DataEntry
dec := json.NewDecoder(request.Body)
dec.Decode(&entry)

// Compute the computed fields
entry.Compute()

---

Is there a better way to do this? Could I use create my own UnmarshalJSON and use that as a trigger to automatically compute the FullName field?

Answer 1

In this case I would just turn FullName into a method. But if you really need to make it that way, just create a wrapper type that is also a json.Unmarshaler:

type DataEntryForJSON DataEntry

func (d *DataEntryForJSON) UnmarshalJSON(b []byte) error {
    if err := json.Unmarshal(b, (*DataEntry)(d)); err != nil {
        return err
    }
    d.FullName = d.FirstName + " " + d.LastName
    return nil
}

Playground: http://play.golang.org/p/g9BnytB5DG.