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cockpit-cache.html
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---
layout: guide
---
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>cockpit.js: Object Cache</title>
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<div class="refentry">
<a name="cockpit-cache"></a><div class="titlepage"></div>
<div class="refnamediv"><table width="100%"><tr>
<td valign="top">
<h2>cockpit.js: Object Cache</h2>
<p>cockpit.js: Object Cache — Caching and sharing data</p>
</td>
<td valign="top" align="right"></td>
</tr></table></div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<p>If the same information is displayed by multiple components in Cockpit,
<code class="code">cockpit.cache()</code> provides a way to share data between them. The shared
data should be simple objects, arrays, and values, and not contain functions or
other objects.</p>
</div>
<div class="refsection">
<a name="cockpit-cache-func"></a><h2>cockpit.cache()</h2>
<pre class="programlisting">
cache = cockpit.cache(key, provider, consumer)
</pre>
<p>Create a new cache object. The <code class="code">key</code> should be a globally unique string
that describes the data being cached. This string must describe the data, across all
machines and all versions of cockpit. It is customary to include a version number in
the <code class="code">key</code> string.</p>
<pre class="programlisting">
function provider(result, key) {
result("myvalue");
return {
close: function() {
/* closed */
}
};
}
</pre>
<p>The <code class="code">provider</code> is a function that will be invoked to start retrieving
data for the cache. It will be passed a <code class="code">result</code> function as its first
argument. The <code class="code">result</code> should be invoked whenever new data is available.
The <code class="code">key</code> argument matches the key string the cache was created with.</p>
<p>The <code class="code">provider</code> can return an object with a <code class="code">close</code> method.
This method will be invoked when the cache no longer needs data from the provider.</p>
<pre class="programlisting">
function consumer(value, key) {
/* ... */
}
</pre>
<p>The <code class="code">consumer</code> is a function that will be passed new values when they
are available, whether they come from the <code class="code">provider</code> or a source in a
different component/frame.</p>
</div>
<div class="refsection">
<a name="cockpit-cache-close"></a><h2>cache.close()</h2>
<pre class="programlisting">
cache.close()
</pre>
<p>Close a cache and stop calling its <code class="code">consumer</code>. If the <code class="code">provider</code>
was invoked, then the <code class="code">close()</code> method it returned will be invoked.</p>
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