How to marshal an empty json object without omitting it?

[yic...@gmail.com]

Hello,

How do I marshal a struct field as an empty json object? For example, 

type Person struct {
    Name string `json:"name"`
    Meta map[string]interface{} `json:"meta"`
}

When I marshal this struct to JSON, I would like to keep the "meta" field as empty json object, like "{}", if it is an empty map,  instead of null or being omitted (using omitempty). 

{
    "name" : "tester",
    "meta": {}
}

Here is the quick sample in playground: http://play.golang.org/p/VRtnY8Ww2s

Thanks!

[Yves Junqueira]

Your question refers to an "empty map", but then you didn't provide the map at all. There's a difference between an empty map and a nil map. This works:

p := Person{

Name: "tester",

Meta: map[string]interface{}{}, // the map is non-nil, but empty.

}

And has the effect of producing:

{
    "name": "tester",
    "meta": {}
}

I hope that helps.

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Yves Junqueira <http://google.com/+YvesJunqueira>