1 // Copyright 2016 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 package json_test 6 7 import ( 8 "encoding/json" 9 "fmt" 10 "log" 11 "strings" 12 ) 13 14 type Animal int 15 16 const ( 17 Unknown Animal = iota 18 Gopher 19 Zebra 20 ) 21 22 func (a *Animal) UnmarshalJSON(b []byte) error { 23 var s string 24 if err := json.Unmarshal(b, &s); err != nil { 25 return err 26 } 27 switch strings.ToLower(s) { 28 default: 29 *a = Unknown 30 case "gopher": 31 *a = Gopher 32 case "zebra": 33 *a = Zebra 34 } 35 36 return nil 37 } 38 39 func (a Animal) MarshalJSON() ([]byte, error) { 40 var s string 41 switch a { 42 default: 43 s = "unknown" 44 case Gopher: 45 s = "gopher" 46 case Zebra: 47 s = "zebra" 48 } 49 50 return json.Marshal(s) 51 } 52 53 func Example_customMarshalJSON() { 54 blob := `["gopher","armadillo","zebra","unknown","gopher","bee","gopher","zebra"]` 55 var zoo []Animal 56 if err := json.Unmarshal([]byte(blob), &zoo); err != nil { 57 log.Fatal(err) 58 } 59 60 census := make(map[Animal]int) 61 for _, animal := range zoo { 62 census[animal] += 1 63 } 64 65 fmt.Printf("Zoo Census:\n* Gophers: %d\n* Zebras: %d\n* Unknown: %d\n", 66 census[Gopher], census[Zebra], census[Unknown]) 67 68 // Output: 69 // Zoo Census: 70 // * Gophers: 3 71 // * Zebras: 2 72 // * Unknown: 3 73 } 74
