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<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Go by Example: XML</title>
<link rel=stylesheet href="site.css">
</head>
<script>
onkeydown = (e) => {
if (e.key == "ArrowLeft") {
window.location.href = 'json';
}
if (e.key == "ArrowRight") {
window.location.href = 'time';
}
}
</script>
<body>
<div class="example" id="xml">
<h2><a href="./">Go by Example</a>: XML</h2>
<table>
<tr>
<td class="docs">
<p>Go offers built-in support for XML and XML-like
formats with the <code>encoding.xml</code> package.</p>
</td>
<td class="code empty leading">
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<a href="http://play.golang.org/p/RsNLhMBazeX"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
<pre class="chroma"><span class="kn">package</span> <span class="nx">main</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kn">import</span> <span class="p">(</span>
<span class="s">"encoding/xml"</span>
<span class="s">"fmt"</span>
<span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>Plant will be mapped to XML. Similarly to the
JSON examples, field tags contain directives for the
encoder and decoder. Here we use some special features
of the XML package: the <code>XMLName</code> field name dictates
the name of the XML element representing this struct;
<code>id,attr</code> means that the <code>Id</code> field is an XML
<em>attribute</em> rather than a nested element.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="kd">type</span> <span class="nx">Plant</span> <span class="kd">struct</span> <span class="p">{</span>
<span class="nx">XMLName</span> <span class="nx">xml</span><span class="p">.</span><span class="nx">Name</span> <span class="s">`xml:"plant"`</span>
<span class="nx">Id</span> <span class="kt">int</span> <span class="s">`xml:"id,attr"`</span>
<span class="nx">Name</span> <span class="kt">string</span> <span class="s">`xml:"name"`</span>
<span class="nx">Origin</span> <span class="p">[]</span><span class="kt">string</span> <span class="s">`xml:"origin"`</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kd">func</span> <span class="p">(</span><span class="nx">p</span> <span class="nx">Plant</span><span class="p">)</span> <span class="nf">String</span><span class="p">()</span> <span class="kt">string</span> <span class="p">{</span>
<span class="k">return</span> <span class="nx">fmt</span><span class="p">.</span><span class="nf">Sprintf</span><span class="p">(</span><span class="s">"Plant id=%v, name=%v, origin=%v"</span><span class="p">,</span>
<span class="nx">p</span><span class="p">.</span><span class="nx">Id</span><span class="p">,</span> <span class="nx">p</span><span class="p">.</span><span class="nx">Name</span><span class="p">,</span> <span class="nx">p</span><span class="p">.</span><span class="nx">Origin</span><span class="p">)</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"><span class="kd">func</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
<span class="nx">coffee</span> <span class="o">:=</span> <span class="o">&</span><span class="nx">Plant</span><span class="p">{</span><span class="nx">Id</span><span class="p">:</span> <span class="mi">27</span><span class="p">,</span> <span class="nx">Name</span><span class="p">:</span> <span class="s">"Coffee"</span><span class="p">}</span>
<span class="nx">coffee</span><span class="p">.</span><span class="nx">Origin</span> <span class="p">=</span> <span class="p">[]</span><span class="kt">string</span><span class="p">{</span><span class="s">"Ethiopia"</span><span class="p">,</span> <span class="s">"Brazil"</span><span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>Emit XML representing our plant; using
<code>MarshalIndent</code> to produce a more
human-readable output.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">out</span><span class="p">,</span> <span class="nx">_</span> <span class="o">:=</span> <span class="nx">xml</span><span class="p">.</span><span class="nf">MarshalIndent</span><span class="p">(</span><span class="nx">coffee</span><span class="p">,</span> <span class="s">" "</span><span class="p">,</span> <span class="s">" "</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">out</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>To add a generic XML header to the output, append
it explicitly.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">xml</span><span class="p">.</span><span class="nx">Header</span> <span class="o">+</span> <span class="nb">string</span><span class="p">(</span><span class="nx">out</span><span class="p">))</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>Use <code>Unmarhshal</code> to parse a stream of bytes with XML
into a data structure. If the XML is malformed or
cannot be mapped onto Plant, a descriptive error
will be returned.</p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="kd">var</span> <span class="nx">p</span> <span class="nx">Plant</span>
<span class="k">if</span> <span class="nx">err</span> <span class="o">:=</span> <span class="nx">xml</span><span class="p">.</span><span class="nf">Unmarshal</span><span class="p">(</span><span class="nx">out</span><span class="p">,</span> <span class="o">&</span><span class="nx">p</span><span class="p">);</span> <span class="nx">err</span> <span class="o">!=</span> <span class="kc">nil</span> <span class="p">{</span>
<span class="nb">panic</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
<span class="p">}</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nx">p</span><span class="p">)</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"> <span class="nx">tomato</span> <span class="o">:=</span> <span class="o">&</span><span class="nx">Plant</span><span class="p">{</span><span class="nx">Id</span><span class="p">:</span> <span class="mi">81</span><span class="p">,</span> <span class="nx">Name</span><span class="p">:</span> <span class="s">"Tomato"</span><span class="p">}</span>
<span class="nx">tomato</span><span class="p">.</span><span class="nx">Origin</span> <span class="p">=</span> <span class="p">[]</span><span class="kt">string</span><span class="p">{</span><span class="s">"Mexico"</span><span class="p">,</span> <span class="s">"California"</span><span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
<p>The <code>parent>child>plant</code> field tag tells the encoder
to nest all <code>plant</code>s under <code><parent><child>...</code></p>
</td>
<td class="code leading">
<pre class="chroma">
<span class="kd">type</span> <span class="nx">Nesting</span> <span class="kd">struct</span> <span class="p">{</span>
<span class="nx">XMLName</span> <span class="nx">xml</span><span class="p">.</span><span class="nx">Name</span> <span class="s">`xml:"nesting"`</span>
<span class="nx">Plants</span> <span class="p">[]</span><span class="o">*</span><span class="nx">Plant</span> <span class="s">`xml:"parent>child>plant"`</span>
<span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code leading">
<pre class="chroma"> <span class="nx">nesting</span> <span class="o">:=</span> <span class="o">&</span><span class="nx">Nesting</span><span class="p">{}</span>
<span class="nx">nesting</span><span class="p">.</span><span class="nx">Plants</span> <span class="p">=</span> <span class="p">[]</span><span class="o">*</span><span class="nx">Plant</span><span class="p">{</span><span class="nx">coffee</span><span class="p">,</span> <span class="nx">tomato</span><span class="p">}</span>
</pre>
</td>
</tr>
<tr>
<td class="docs">
</td>
<td class="code">
<pre class="chroma"> <span class="nx">out</span><span class="p">,</span> <span class="nx">_</span> <span class="p">=</span> <span class="nx">xml</span><span class="p">.</span><span class="nf">MarshalIndent</span><span class="p">(</span><span class="nx">nesting</span><span class="p">,</span> <span class="s">" "</span><span class="p">,</span> <span class="s">" "</span><span class="p">)</span>
<span class="nx">fmt</span><span class="p">.</span><span class="nf">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">out</span><span class="p">))</span>
<span class="p">}</span>
</pre>
</td>
</tr>
</table>
<table>
<tr>
<td class="docs">
</td>
<td class="code">
<pre class="chroma"><span class="gp">$</span> go run xml.go
<span class="go"> <plant id="27">
</span><span class="go"> <name>Coffee</name>
</span><span class="go"> <origin>Ethiopia</origin>
</span><span class="go"> <origin>Brazil</origin>
</span><span class="go"> </plant>
</span><span class="go"><?xml version="1.0" encoding="UTF-8"?>
</span><span class="go"> <plant id="27">
</span><span class="go"> <name>Coffee</name>
</span><span class="go"> <origin>Ethiopia</origin>
</span><span class="go"> <origin>Brazil</origin>
</span><span class="go"> </plant>
</span><span class="go">Plant id=27, name=Coffee, origin=[Ethiopia Brazil]
</span><span class="go"> <nesting>
</span><span class="go"> <parent>
</span><span class="go"> <child>
</span><span class="go"> <plant id="27">
</span><span class="go"> <name>Coffee</name>
</span><span class="go"> <origin>Ethiopia</origin>
</span><span class="go"> <origin>Brazil</origin>
</span><span class="go"> </plant>
</span><span class="go"> <plant id="81">
</span><span class="go"> <name>Tomato</name>
</span><span class="go"> <origin>Mexico</origin>
</span><span class="go"> <origin>California</origin>
</span><span class="go"> </plant>
</span><span class="go"> </child>
</span><span class="go"> </parent>
</span><span class="go"> </nesting></span></pre>
</td>
</tr>
</table>
<p class="next">
Next example: <a href="time">Time</a>.
</p>
<p class="footer">
by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> and <a href="https://eli.thegreenplace.net">Eli Bendersky</a> | <a href="https://github.com/mmcgrana/gobyexample">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
</p>
</div>
<script>
var codeLines = [];
codeLines.push('');codeLines.push('package main\u000A');codeLines.push('import (\u000A \"encoding/xml\"\u000A \"fmt\"\u000A)\u000A');codeLines.push('type Plant struct {\u000A XMLName xml.Name `xml:\"plant\"`\u000A Id int `xml:\"id,attr\"`\u000A Name string `xml:\"name\"`\u000A Origin []string `xml:\"origin\"`\u000A}\u000A');codeLines.push('func (p Plant) String() string {\u000A return fmt.Sprintf(\"Plant id\u003D%v, name\u003D%v, origin\u003D%v\",\u000A p.Id, p.Name, p.Origin)\u000A}\u000A');codeLines.push('func main() {\u000A coffee :\u003D \u0026Plant{Id: 27, Name: \"Coffee\"}\u000A coffee.Origin \u003D []string{\"Ethiopia\", \"Brazil\"}\u000A');codeLines.push(' out, _ :\u003D xml.MarshalIndent(coffee, \" \", \" \")\u000A fmt.Println(string(out))\u000A');codeLines.push(' fmt.Println(xml.Header + string(out))\u000A');codeLines.push(' var p Plant\u000A if err :\u003D xml.Unmarshal(out, \u0026p); err !\u003D nil {\u000A panic(err)\u000A }\u000A fmt.Println(p)\u000A');codeLines.push(' tomato :\u003D \u0026Plant{Id: 81, Name: \"Tomato\"}\u000A tomato.Origin \u003D []string{\"Mexico\", \"California\"}\u000A');codeLines.push(' type Nesting struct {\u000A XMLName xml.Name `xml:\"nesting\"`\u000A Plants []*Plant `xml:\"parent\u003Echild\u003Eplant\"`\u000A }\u000A');codeLines.push(' nesting :\u003D \u0026Nesting{}\u000A nesting.Plants \u003D []*Plant{coffee, tomato}\u000A');codeLines.push(' out, _ \u003D xml.MarshalIndent(nesting, \" \", \" \")\u000A fmt.Println(string(out))\u000A}\u000A');codeLines.push('');
</script>
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