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Unmarshal JSON to specific interface implementation
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| package main | |
| import ( | |
| "encoding/json" | |
| "fmt" | |
| "reflect" | |
| ) | |
| type Something interface{} | |
| type Something1 struct { | |
| Aaa, Bbb string | |
| } | |
| type Something2 struct { | |
| Ccc, Ddd string | |
| } | |
| var _ Something = (*Something1)(nil) | |
| var _ Something = (*Something2)(nil) | |
| func UnmarshalCustomValue(data []byte, typeJsonField, valueJsonField string, customTypes map[string]reflect.Type) (interface{}, error) { | |
| m := map[string]interface{}{} | |
| if err := json.Unmarshal(data, &m); err != nil { | |
| return nil, err | |
| } | |
| typeName := m[typeJsonField].(string) | |
| var value Something | |
| if ty, found := customTypes[typeName]; found { | |
| value = reflect.New(ty).Interface().(Something) | |
| } | |
| valueBytes, err := json.Marshal(m[valueJsonField]) | |
| if err != nil { | |
| return nil, err | |
| } | |
| err = json.Unmarshal(valueBytes, &value) | |
| if err != nil { | |
| return nil, err | |
| } | |
| return value, nil | |
| } | |
| type Container struct { | |
| Type string `json:"type"` | |
| Value Something `json:"value"` | |
| } | |
| func (c *Container) UnmarshalJSON(data []byte) error { | |
| value, err := UnmarshalCustomValue(data, "type", "value", map[string]reflect.Type{ | |
| "something1": reflect.TypeOf(Something1{}), | |
| "something2": reflect.TypeOf(Something2{}), | |
| }) | |
| if err != nil { | |
| return err | |
| } | |
| c.Value = value | |
| return nil | |
| } | |
| var _ json.Unmarshaler = (*Container)(nil) | |
| func panicIfErr(err error) { | |
| if err != nil { | |
| panic(err.Error()) | |
| } | |
| } | |
| func main() { | |
| testUnmarshalling(`{"type":"something1","value":{"Aaa": "a"}}`) | |
| testUnmarshalling(`{"type":"something2","value":{"Ccc": "a"}}`) | |
| } | |
| func testUnmarshalling(jsonStr string) { | |
| var container Container | |
| err := json.Unmarshal([]byte(jsonStr), &container) | |
| panicIfErr(err) | |
| fmt.Printf("container=%+v\n", container) | |
| fmt.Printf("value=%#v\n", container.Value) | |
| } |
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