shard-crystal-db/api/0.9.0/DB/Serializable.html
2020-09-30 17:51:30 -03:00

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<h1 class="type-name">
<span class="kind">module</span> DB::Serializable
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Overview
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<p>The <code>DB::Serialization</code> module automatically generates methods for DB serialization when included.</p>
<p>Once included, <code><a href="../DB/ResultSet.html#read(type:DB::Mappable.class)-instance-method">ResultSet#read(t)</a></code> populates properties of the class from the
<code><a href="../DB/ResultSet.html">ResultSet</a></code>.</p>
<h3><a id="example" class="anchor" href="#example">
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<pre><code class="language-crystal"><span class="k">require</span> <span class="s">&quot;db&quot;</span>
<span class="k">class</span> <span class="t">Employee</span>
<span class="k">include</span> <span class="t">DB</span><span class="t">::</span><span class="t">Serializable</span>
property title : <span class="t">String</span>
property name : <span class="t">String</span>
<span class="k">end</span>
employees <span class="o">=</span> <span class="t">Employee</span>.from_rs(db.query(<span class="s">&quot;SELECT title, name FROM employees&quot;</span>))
employees[<span class="n">0</span>].title <span class="c"># =&gt; &quot;Manager&quot;</span>
employees[<span class="n">0</span>].name <span class="c"># =&gt; &quot;John&quot;</span></code></pre>
<h3><a id="usage" class="anchor" href="#usage">
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<p><code><a href="../DB/Serializable.html">DB::Serializable</a></code> was designed in analogue with <code>JSON::Serializable</code>, so usage is identical.
However, like <code><a href="../DB.html#mapping(**properties)-macro">DB.mapping</a></code>, <code><a href="../DB/Serializable.html">DB::Serializable</a></code> is <strong>strict by default</strong>, so extra columns will raise <code><a href="../DB/MappingException.html">DB::MappingException</a></code>s.</p>
<p>Similar to <code>JSON::Field</code>, there is an annotation <code><a href="../DB/Field.html">DB::Field</a></code> that can be used to set serialization behavior
on individual instance variables.</p>
<pre><code class="language-crystal"><span class="k">class</span> <span class="t">Employee</span>
<span class="k">include</span> <span class="t">DB</span><span class="t">::</span><span class="t">Serializable</span>
property title : <span class="t">String</span>
@[<span class="t">DB</span><span class="t">::</span><span class="t">Field</span>(key: <span class="s">&quot;firstname&quot;</span>)]
property name : <span class="t">String</span>?
<span class="k">end</span></code></pre>
<p><code><a href="../DB/Field.html">DB::Field</a></code> properties:</p>
<ul><li><strong>ignore</strong>: if <code>true</code>, skip this field in serialization and deserialization (<code>false</code> by default)</li><li><strong>key</strong>: defines which column to read from a <code><a href="../DB/ResultSet.html">ResultSet</a></code> (name of the instance variable by default)</li><li><strong>converter</strong>: defines an alternate type for parsing results. The given type must define <code>#from_rs(DB::ResultSet)</code> and return an instance of the included type.</li></ul>
<h3><a id="dbserializablenon-strict" class="anchor" href="#dbserializablenon-strict">
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</a><code><a href="../DB/Serializable/NonStrict.html">DB::Serializable::NonStrict</a></code></h3>
<p>Including this module is functionally identical to passing <code>{strict: false}</code> to <code><a href="../DB.html#mapping(**properties)-macro">DB.mapping</a></code>: extra columns will not raise.</p>
<pre><code class="language-crystal"><span class="k">class</span> <span class="t">Employee</span>
<span class="k">include</span> <span class="t">DB</span><span class="t">::</span><span class="t">Serializable</span>
<span class="k">include</span> <span class="t">DB</span><span class="t">::</span><span class="t">Serializable</span><span class="t">::</span><span class="t">NonStrict</span>
property title : <span class="t">String</span>
property name : <span class="t">String</span>
<span class="k">end</span>
<span class="c"># does not raise!</span>
employees <span class="o">=</span> <span class="t">Employee</span>.from_rs(db.query(<span class="s">&quot;SELECT title, name, age FROM employees&quot;</span>))</code></pre>
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Defined in:
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Constructors
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<a href="#new(*,__set_for_db_serializablers:DB::ResultSet)-class-method" class="signature"><strong>.new</strong>(*, __set_for_db_serializable rs : DB::ResultSet)</a>
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Constructor Detail
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def self.<strong>new</strong>(*, __set_for_db_serializable rs : <a href="../DB/ResultSet.html">DB::ResultSet</a>)
<a class="method-permalink" href="#new(*,__set_for_db_serializablers:DB::ResultSet)-class-method">#</a>
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