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Source file src/encoding/json/example_marshaling_test.go

Documentation: encoding/json

     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  

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