Golang JSON的进阶用法实例讲解

{
 "name":"yulibaozi",
 "port":8080
}

type Host struct {
 Name string `json:"name"`
 Port Port `json:"port"`
}

type Type int

const (
 Int Type = iota
 String
)

type Port struct {
 Type Type
 IntVal int
 StrVal string
}

json.Unmarshaller interface
json.Marshaller interface

type Port struct {
 Type Type
 IntVal int
 StrVal string
}

// 实现 json.Unmarshaller 接口
func (port *Port) UnmarshalJSON(value []byte) error {
 if value[0] == '"' {
  port.Type = String
  return json.Unmarshal(value, &port.StrVal)
 }
 port.Type = Int
 return json.Unmarshal(value, &port.IntVal)
}

// 实现 json.Marshaller 接口
func (port Port) MarshalJSON() ([]byte, error) {
 switch port.Type {
 case Int:
  return json.Marshal(port.IntVal)
 case String:
  return json.Marshal(port.StrVal)
 default:
  return []byte{}, fmt.Errorf("impossible Port.Type")
 }
}

{"name":"yulibaozi","port":8090}

&{Name:yulibaozi Port:{Type:0 IntVal:8090 StrVal:}}

{"name":"yulibaozi","port":"8090"}

&{Name:yulibaozi Port:{Type:1 IntVal:0 StrVal:8090}}

host := &Host{
   Name: "yulibaozi",
   Port: Port{
     Type:  Int,
     IntVal: 8080,
   },
 }

{"name":"yulibaozi","port":8080}

host := &Host{
   Name: "yulibaozi",
   Port: Port{
     Type:  String,
     StrVal: "8080",
   },
 }

{"name":"yulibaozi","port":"8080"}