289 lines
15 KiB
Plaintext
Generated
289 lines
15 KiB
Plaintext
Generated
<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8">
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<title>Go by Example: XML</title>
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<link rel=stylesheet href="site.css">
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</head>
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<script>
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onkeydown = (e) => {
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<div class="example" id="xml">
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<h2><a href="./">Go by Example</a>: XML</h2>
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<table>
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<tr>
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<td class="docs">
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<p>Go offers built-in support for XML and XML-like
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formats with the <code>encoding.xml</code> package.</p>
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</td>
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<td class="code empty leading">
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<td class="docs">
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<td class="code leading">
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<a href="http://play.golang.org/p/qd9Ii_3AW0s"><img title="Run code" src="play.png" class="run" /></a><img title="Copy code" src="clipboard.png" class="copy" />
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<div class="highlight"><pre><span class="kn">package</span> <span class="nx">main</span>
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</pre></div>
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</td>
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</tr>
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<td class="docs">
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<td class="code leading">
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<div class="highlight"><pre><span class="kn">import</span> <span class="p">(</span>
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<span class="s">"encoding/xml"</span>
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<span class="s">"fmt"</span>
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<span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>This type will be mapped to XML. Similarly to the
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JSON examples, field tags contain directives for the
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encoder and decoder. Here we use some special features
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of the XML package: the <code>XMLName</code> field name dictates
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the name of the XML element representing this struct;
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<code>id,attr</code> means that the <code>Id</code> field is an XML
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<em>attribute</em> rather than a nested element.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre><span class="kd">type</span> <span class="nx">Plant</span> <span class="kd">struct</span> <span class="p">{</span>
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<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>
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<span class="nx">Id</span> <span class="kt">int</span> <span class="s">`xml:"id,attr"`</span>
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<span class="nx">Name</span> <span class="kt">string</span> <span class="s">`xml:"name"`</span>
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<span class="nx">Origin</span> <span class="p">[]</span><span class="kt">string</span> <span class="s">`xml:"origin"`</span>
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<span class="p">}</span>
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</pre></div>
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<div class="highlight"><pre><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="nx">String</span><span class="p">()</span> <span class="kt">string</span> <span class="p">{</span>
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<span class="k">return</span> <span class="nx">fmt</span><span class="p">.</span><span class="nx">Sprintf</span><span class="p">(</span><span class="s">"Plant id=%v, name=%v, origin=%v"</span><span class="p">,</span>
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<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>
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<span class="p">}</span>
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</pre></div>
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</td>
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</tr>
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<div class="highlight"><pre><span class="kd">func</span> <span class="nx">main</span><span class="p">()</span> <span class="p">{</span>
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<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>
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<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>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Emit XML representing our plant; using
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<code>MarshalIndent</code> to produce a more
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human-readable output.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <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="nx">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>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">out</span><span class="p">))</span>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>To add a generic XML header to the output, append
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it explicitly.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="nx">fmt</span><span class="p">.</span><span class="nx">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>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>Use <code>Unmarhshal</code> to parse a stream of bytes with XML
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into a data structure. If the XML is malformed or
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cannot be mapped onto Plant, a descriptive error
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will be returned.</p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="kd">var</span> <span class="nx">p</span> <span class="nx">Plant</span>
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<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="nx">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>
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<span class="nb">panic</span><span class="p">(</span><span class="nx">err</span><span class="p">)</span>
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<span class="p">}</span>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nx">p</span><span class="p">)</span>
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</pre></div>
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</td>
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</tr>
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<td class="docs">
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<td class="code leading">
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<div class="highlight"><pre> <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>
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<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>
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</pre></div>
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</td>
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</tr>
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<tr>
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<td class="docs">
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<p>The <code>parent>child>plant</code> field tag tells the encoder
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to nest all <code>plant</code>s under <code><parent><child>...</code></p>
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</td>
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<td class="code leading">
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<div class="highlight"><pre> <span class="kd">type</span> <span class="nx">Nesting</span> <span class="kd">struct</span> <span class="p">{</span>
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<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>
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<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>
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<span class="p">}</span>
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</pre></div>
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</td>
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<div class="highlight"><pre> <span class="nx">nesting</span> <span class="o">:=</span> <span class="o">&</span><span class="nx">Nesting</span><span class="p">{}</span>
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<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>
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</pre></div>
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<td class="code">
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<div class="highlight"><pre> <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="nx">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>
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<span class="nx">fmt</span><span class="p">.</span><span class="nx">Println</span><span class="p">(</span><span class="nb">string</span><span class="p">(</span><span class="nx">out</span><span class="p">))</span>
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<span class="p">}</span>
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</pre></div>
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</td>
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</table>
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<table>
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<td class="code">
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<div class="highlight"><pre><span class="gp">$</span> go run xml.go
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<span class="go"> <plant id="27"></span>
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<span class="go"> <name>Coffee</name></span>
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<span class="go"> <origin>Ethiopia</origin></span>
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<span class="go"> <origin>Brazil</origin></span>
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<span class="go"> </plant></span>
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<span class="go"><?xml version="1.0" encoding="UTF-8"?></span>
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<span class="go"> <plant id="27"></span>
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<span class="go"> <name>Coffee</name></span>
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<span class="go"> <origin>Ethiopia</origin></span>
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<span class="go"> <origin>Brazil</origin></span>
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<span class="go"> </plant></span>
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<span class="go">Plant id=27, name=Coffee, origin=[Ethiopia Brazil]</span>
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<span class="go"> <nesting></span>
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<span class="go"> <parent></span>
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<span class="go"> <child></span>
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<span class="go"> <plant id="27"></span>
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<span class="go"> <name>Coffee</name></span>
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<span class="go"> <origin>Ethiopia</origin></span>
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<span class="go"> <origin>Brazil</origin></span>
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<span class="go"> </plant></span>
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<span class="go"> <plant id="81"></span>
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<span class="go"> <name>Tomato</name></span>
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<span class="go"> <origin>Mexico</origin></span>
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<span class="go"> <origin>California</origin></span>
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<span class="go"> </plant></span>
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<span class="go"> </child></span>
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<span class="go"> </parent></span>
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<span class="go"> </nesting></span>
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</pre></div>
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</td>
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</table>
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<p class="next">
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Next example: <a href="time">Time</a>.
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</p>
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<p class="footer">
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by <a href="https://markmcgranaghan.com">Mark McGranaghan</a> | <a href="https://github.com/mmcgrana/gobyexample/blob/master/examples/xml">source</a> | <a href="https://github.com/mmcgrana/gobyexample#license">license</a>
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</p>
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</div>
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<script>
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var codeLines = [];
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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=%v, name=%v, origin=%v\",\u000A p.Id, p.Name, p.Origin)\u000A}\u000A');codeLines.push('func main() {\u000A coffee := &Plant{Id: 27, Name: \"Coffee\"}\u000A coffee.Origin = []string{\"Ethiopia\", \"Brazil\"}\u000A');codeLines.push(' out, _ := 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 := xml.Unmarshal(out, &p); err != nil {\u000A panic(err)\u000A }\u000A fmt.Println(p)\u000A');codeLines.push(' tomato := &Plant{Id: 81, Name: \"Tomato\"}\u000A tomato.Origin = []string{\"Mexico\", \"California\"}\u000A');codeLines.push(' type Nesting struct {\u000A XMLName xml.Name `xml:\"nesting\"`\u000A Plants []*Plant `xml:\"parent\x3Echild\x3Eplant\"`\u000A }\u000A');codeLines.push(' nesting := &Nesting{}\u000A nesting.Plants = []*Plant{coffee, tomato}\u000A');codeLines.push(' out, _ = xml.MarshalIndent(nesting, \" \", \" \")\u000A fmt.Println(string(out))\u000A}\u000A');codeLines.push('');
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</script>
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<script src="site.js" async></script>
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