example_marshaling_test.go

     1  // Copyright 2018 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 xml_test
     6  
     7  import (
     8  	"encoding/xml"
     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) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
    23  	var s string
    24  	if err := d.DecodeElement(&s, &start); 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) MarshalXML(e *xml.Encoder, start xml.StartElement) 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  	return e.EncodeElement(s, start)
    50  }
    51  
    52  func Example_customMarshalXML() {
    53  	blob := `
    54  	<animals>
    55  		<animal>gopher</animal>
    56  		<animal>armadillo</animal>
    57  		<animal>zebra</animal>
    58  		<animal>unknown</animal>
    59  		<animal>gopher</animal>
    60  		<animal>bee</animal>
    61  		<animal>gopher</animal>
    62  		<animal>zebra</animal>
    63  	</animals>`
    64  	var zoo struct {
    65  		Animals []Animal `xml:"animal"`
    66  	}
    67  	if err := xml.Unmarshal([]byte(blob), &zoo); err != nil {
    68  		log.Fatal(err)
    69  	}
    70  
    71  	census := make(map[Animal]int)
    72  	for _, animal := range zoo.Animals {
    73  		census[animal] += 1
    74  	}
    75  
    76  	fmt.Printf("Zoo Census:\n* Gophers: %d\n* Zebras:  %d\n* Unknown: %d\n",
    77  		census[Gopher], census[Zebra], census[Unknown])
    78  
    79  	// Output:
    80  	// Zoo Census:
    81  	// * Gophers: 3
    82  	// * Zebras:  2
    83  	// * Unknown: 3
    84  }
    85
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