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<?xml version="1.0"?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
"http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd">
<refentry id="cockpit-cache">
<refnamediv>
<refname>cockpit.js: Object Cache</refname>
<refpurpose>Caching and sharing data</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para>If the same information is displayed by multiple components in Cockpit,
<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.</para>
</refsynopsisdiv>
<refsection id="cockpit-cache-func">
<title>cockpit.cache()</title>
<programlisting>
cache = cockpit.cache(key, provider, consumer)
</programlisting>
<para>Create a new cache object. The <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>key</code> string.</para>
<programlisting>
function provider(result, key) {
result("myvalue");
return {
close: function() {
/* closed */
}
};
}
</programlisting>
<para>The <code>provider</code> is a function that will be invoked to start retrieving
data for the cache. It will be passed a <code>result</code> function as its first
argument. The <code>result</code> should be invoked whenever new data is available.
The <code>key</code> argument matches the key string the cache was created with.</para>
<para>The <code>provider</code> can return an object with a <code>close</code> method.
This method will be invoked when the cache no longer needs data from the provider.</para>
<programlisting>
function consumer(value, key) {
/* ... */
}
</programlisting>
<para>The <code>consumer</code> is a function that will be passed new values when they
are available, whether they come from the <code>provider</code> or a source in a
different component/frame.</para>
</refsection>
<refsection id="cockpit-cache-close">
<title>cache.close()</title>
<programlisting>
cache.close()
</programlisting>
<para>Close a cache and stop calling its <code>consumer</code>. If the <code>provider</code>
was invoked, then the <code>close()</code> method it returned will be invoked.</para>
</refsection>
</refentry>
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