v2_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  //go:build goexperiment.jsonv2
     6  
     7  package json_test
     8  
     9  import (
    10  	"fmt"
    11  	"log"
    12  	"strings"
    13  
    14  	"encoding/json"
    15  )
    16  
    17  type Animal int
    18  
    19  const (
    20  	Unknown Animal = iota
    21  	Gopher
    22  	Zebra
    23  )
    24  
    25  func (a *Animal) UnmarshalJSON(b []byte) error {
    26  	var s string
    27  	if err := json.Unmarshal(b, &s); err != nil {
    28  		return err
    29  	}
    30  	switch strings.ToLower(s) {
    31  	default:
    32  		*a = Unknown
    33  	case "gopher":
    34  		*a = Gopher
    35  	case "zebra":
    36  		*a = Zebra
    37  	}
    38  
    39  	return nil
    40  }
    41  
    42  func (a Animal) MarshalJSON() ([]byte, error) {
    43  	var s string
    44  	switch a {
    45  	default:
    46  		s = "unknown"
    47  	case Gopher:
    48  		s = "gopher"
    49  	case Zebra:
    50  		s = "zebra"
    51  	}
    52  
    53  	return json.Marshal(s)
    54  }
    55  
    56  func Example_customMarshalJSON() {
    57  	blob := `["gopher","armadillo","zebra","unknown","gopher","bee","gopher","zebra"]`
    58  	var zoo []Animal
    59  	if err := json.Unmarshal([]byte(blob), &zoo); err != nil {
    60  		log.Fatal(err)
    61  	}
    62  
    63  	census := make(map[Animal]int)
    64  	for _, animal := range zoo {
    65  		census[animal] += 1
    66  	}
    67  
    68  	fmt.Printf("Zoo Census:\n* Gophers: %d\n* Zebras:  %d\n* Unknown: %d\n",
    69  		census[Gopher], census[Zebra], census[Unknown])
    70  
    71  	// Output:
    72  	// Zoo Census:
    73  	// * Gophers: 3
    74  	// * Zebras:  2
    75  	// * Unknown: 3
    76  }
    77
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