libgo/go/encoding/json/example_marshaling_test.go

   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 // +build ignore
   6
   7 package json_test
   8
   9 import (
  10         "encoding/json"
  11         "fmt"
  12         "log"
  13         "strings"
  14 )
  15
  16 type Animal int
  17
  18 const (
  19         Unknown Animal = iota
  20         Gopher
  21         Zebra
  22 )
  23
  24 func (a *Animal) UnmarshalJSON(b []byte) error {
  25         var s string
  26         if err := json.Unmarshal(b, &s); err != nil {
  27                 return err
  28         }
  29         switch strings.ToLower(s) {
  30         default:
  31                 *a = Unknown
  32         case "gopher":
  33                 *a = Gopher
  34         case "zebra":
  35                 *a = Zebra
  36         }
  37
  38         return nil
  39 }
  40
  41 func (a Animal) MarshalJSON() ([]byte, error) {
  42         var s string
  43         switch a {
  44         default:
  45                 s = "unknown"
  46         case Gopher:
  47                 s = "gopher"
  48         case Zebra:
  49                 s = "zebra"
  50         }
  51
  52         return json.Marshal(s)
  53 }
  54
  55 func Example_customMarshalJSON() {
  56         blob := `["gopher","armadillo","zebra","unknown","gopher","bee","gopher","zebra"]`
  57         var zoo []Animal
  58         if err := json.Unmarshal([]byte(blob), &zoo); err != nil {
  59                 log.Fatal(err)
  60         }
  61
  62         census := make(map[Animal]int)
  63         for _, animal := range zoo {
  64                 census[animal] += 1
  65         }
  66
  67         fmt.Printf("Zoo Census:\n* Gophers: %d\n* Zebras:  %d\n* Unknown: %d\n",
  68                 census[Gopher], census[Zebra], census[Unknown])
  69
  70         // Output:
  71         // Zoo Census:
  72         // * Gophers: 3
  73         // * Zebras:  2
  74         // * Unknown: 3
  75 }