将结构转换为JSON，其中字段是另一个结构

Question

I have two structs struct:

type A struct {
    Zip string `json:"zip"`
}

type B struct {
    Foo string `bson:"foo"`
    Bar A      `json:"bar"`
}

When I try to json.Marshal the B type, the Bar field does not get converted correctly. The fields are OK, but the values are always empty. The output looks like this:

{"foo": "some-string-value", "bar": {"zip": ""}}

What am I doing wrong?

Answer 1

Your Zip field in A is not populated.

type A struct {
    Zip string `json:"zip"`
}

type B struct {
    Foo string `bson:"foo"`
    Bar A      `json:"bar"`
} 
func main() {
    one := A{"35000"}
    two := B{"Foo", one}
    json, _ := json.Marshal(two)
    fmt.Printf("%s
", json)
}

Output is (https://play.golang.org/p/kyG1YabpSe):

{"Foo":"Foo","bar":{"zip":"35000"}}

Even with a map

type A struct {
   Zip string `json:"zip"`
}
type B struct {
   Foo string `bson:"foo"`
   Bar A      `json:"bar"`
}
func main() {
   m := make(map[string]B)

   for x := 0; x < 10; x++ {
      m[strconv.Itoa(x)] = B{"Hello", A{"35000"}}
   }

   json, _ := json.Marshal(m)
   fmt.Printf("%s
", json)
}

https://play.golang.org/p/qCsmAGzo4H

Output is good, i don't understand where you are wrong.