如何选择性地将JSON编组为结构？

Question

I have a struct:

type Paper struct {
    PID    int    `json:"pID"`
    PTitle string `json:"pTitle"`
    PDesc  string `json:"pDesc"`
    PPwd   string `json:"pPwd"`
}

Mostly, I will encode the entire struct to JSON. However, occasionally, I need the brief version of the struct; i.e. encode some of the properties, how should I implement this feature?

type BriefPaper struct {
    PID    int    `json:"-"`      // not needed
    PTitle string `json:"pTitle"`
    PDesc  string `json:"pDesc"`
    PPwd   string `json:"-"`      // not needed
}

I am thinking of creating a subset struct, something like BriefPaper = SUBSET(Paper), but not sure how to implement it in Golang.

I hope I can do something like this:

p := Paper{ /* ... */ }
pBrief := BriefPaper{}

pBrief = p;
p.MarshalJSON(); // if need full JSON, then marshal Paper
pBrief.MarshalJSON(); // else, only encode some of the required properties

Is it possible?

Answer 1

Probably the easiest way to do this is to create a struct embeds Paper, and shadows the fields you want to hide:

type Paper struct {
    PID    int    `json:"pID"`
    PTitle string `json:"pTitle"`
    PDesc  string `json:"pDesc"`
    PPwd   string `json:"pPwd"`
}

type BriefPaper struct {
    Paper
    PID    int    `json:"pID,omitempty"`  // Just make sure you 
    PPwd   string `json:"pPwd,omitempty"` // don't set these fields!
}

p := Paper{ /* ... */ }
pBrief := BriefPaper{Paper: p}

Now when marshaing BriefPaper, the fields PID and PPwd will be omitted.