EVOLUTION-MANAGER
Edit File: hooks.html
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>The current component registry — zope.configuration 4.0 documentation</title> <link rel="stylesheet" href="_static/default.css" type="text/css" /> <link rel="stylesheet" href="_static/pygments.css" type="text/css" /> <script type="text/javascript"> var DOCUMENTATION_OPTIONS = { URL_ROOT: '', VERSION: '4.0', COLLAPSE_INDEX: false, FILE_SUFFIX: '.html', HAS_SOURCE: true }; </script> <script type="text/javascript" src="_static/jquery.js"></script> <script type="text/javascript" src="_static/underscore.js"></script> <script type="text/javascript" src="_static/doctools.js"></script> <link rel="top" title="zope.configuration 4.0 documentation" href="index.html" /> <link rel="next" title="Layers" href="testlayer.html" /> <link rel="prev" title="Package configuration" href="configure.html" /> </head> <body> <div class="related"> <h3>Navigation</h3> <ul> <li class="right" style="margin-right: 10px"> <a href="genindex.html" title="General Index" accesskey="I">index</a></li> <li class="right" > <a href="testlayer.html" title="Layers" accesskey="N">next</a> |</li> <li class="right" > <a href="configure.html" title="Package configuration" accesskey="P">previous</a> |</li> <li><a href="index.html">zope.configuration 4.0 documentation</a> »</li> </ul> </div> <div class="document"> <div class="documentwrapper"> <div class="bodywrapper"> <div class="body"> <div class="section" id="the-current-component-registry"> <h1>The current component registry<a class="headerlink" href="#the-current-component-registry" title="Permalink to this headline">¶</a></h1> <p>There can be any number of component registries in an application. One of them is the global component registry, and there is also the concept of a currently used component registry. Component registries other than the global one are associated with objects called sites. The <tt class="docutils literal"><span class="pre">zope.component.hooks</span></tt> module provides an API to set and access the current site as well as manipulate the adapter hook associated with it.</p> <p>As long as we haven’t set a site, none is being considered current:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.component.hooks</span> <span class="kn">import</span> <span class="n">getSite</span> <span class="gp">>>> </span><span class="k">print</span> <span class="n">getSite</span><span class="p">()</span> <span class="go">None</span> </pre></div> </div> <p>We can also ask for the current component registry (aka site manager historically); it will return the global one if no current site is set:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.component.hooks</span> <span class="kn">import</span> <span class="n">getSiteManager</span> <span class="gp">>>> </span><span class="n">getSiteManager</span><span class="p">()</span> <span class="go"><BaseGlobalComponents base></span> </pre></div> </div> <p>Let’s set a site now. A site has to be an object that provides the <tt class="docutils literal"><span class="pre">getSiteManager</span></tt> method, which is specified by <tt class="docutils literal"><span class="pre">zope.component.interfaces.IPossibleSite</span></tt>:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.interface.registry</span> <span class="kn">import</span> <span class="n">Components</span> <span class="gp">>>> </span><span class="k">class</span> <span class="nc">Site</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span> <span class="gp">... </span> <span class="k">def</span> <span class="nf">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span> <span class="gp">... </span> <span class="bp">self</span><span class="o">.</span><span class="n">registry</span> <span class="o">=</span> <span class="n">Components</span><span class="p">(</span><span class="s">'components'</span><span class="p">)</span> <span class="gp">... </span> <span class="k">def</span> <span class="nf">getSiteManager</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span> <span class="gp">... </span> <span class="k">return</span> <span class="bp">self</span><span class="o">.</span><span class="n">registry</span> <span class="gp">>>> </span><span class="kn">from</span> <span class="nn">zope.component.hooks</span> <span class="kn">import</span> <span class="n">setSite</span> <span class="gp">>>> </span><span class="n">site1</span> <span class="o">=</span> <span class="n">Site</span><span class="p">()</span> <span class="gp">>>> </span><span class="n">setSite</span><span class="p">(</span><span class="n">site1</span><span class="p">)</span> </pre></div> </div> <p>After this, the newly set site is considered the currently active one:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">getSite</span><span class="p">()</span> <span class="ow">is</span> <span class="n">site1</span> <span class="go">True</span> <span class="gp">>>> </span><span class="n">getSiteManager</span><span class="p">()</span> <span class="ow">is</span> <span class="n">site1</span><span class="o">.</span><span class="n">registry</span> <span class="go">True</span> </pre></div> </div> <p>If we set another site, that one will be considered current:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">site2</span> <span class="o">=</span> <span class="n">Site</span><span class="p">()</span> <span class="gp">>>> </span><span class="n">site2</span><span class="o">.</span><span class="n">registry</span> <span class="ow">is</span> <span class="ow">not</span> <span class="n">site1</span><span class="o">.</span><span class="n">registry</span> <span class="go">True</span> <span class="gp">>>> </span><span class="n">setSite</span><span class="p">(</span><span class="n">site2</span><span class="p">)</span> <span class="gp">>>> </span><span class="n">getSite</span><span class="p">()</span> <span class="ow">is</span> <span class="n">site2</span> <span class="go">True</span> <span class="gp">>>> </span><span class="n">getSiteManager</span><span class="p">()</span> <span class="ow">is</span> <span class="n">site2</span><span class="o">.</span><span class="n">registry</span> <span class="go">True</span> </pre></div> </div> <p>Finally we can unset the site and the global component registry is used again:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">setSite</span><span class="p">()</span> <span class="gp">>>> </span><span class="k">print</span> <span class="n">getSite</span><span class="p">()</span> <span class="go">None</span> <span class="gp">>>> </span><span class="n">getSiteManager</span><span class="p">()</span> <span class="go"><BaseGlobalComponents base></span> </pre></div> </div> <div class="section" id="context-manager"> <h2>Context manager<a class="headerlink" href="#context-manager" title="Permalink to this headline">¶</a></h2> <p>There also is a context manager for setting the site, which is especially useful when writing tests:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">zope.component.hooks</span> <span class="gp">>>> </span><span class="k">print</span> <span class="n">getSite</span><span class="p">()</span> <span class="go">None</span> <span class="gp">>>> </span><span class="k">with</span> <span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">hooks</span><span class="o">.</span><span class="n">site</span><span class="p">(</span><span class="n">site2</span><span class="p">):</span> <span class="gp">... </span> <span class="n">getSite</span><span class="p">()</span> <span class="ow">is</span> <span class="n">site2</span> <span class="go">True</span> <span class="gp">>>> </span><span class="k">print</span> <span class="n">getSite</span><span class="p">()</span> <span class="go">None</span> </pre></div> </div> <p>The site is properly restored even if the body of the with statement raises an exception:</p> <div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="k">print</span> <span class="n">getSite</span><span class="p">()</span> <span class="go">None</span> <span class="gp">>>> </span><span class="k">with</span> <span class="n">zope</span><span class="o">.</span><span class="n">component</span><span class="o">.</span><span class="n">hooks</span><span class="o">.</span><span class="n">site</span><span class="p">(</span><span class="n">site2</span><span class="p">):</span> <span class="gp">... </span> <span class="n">getSite</span><span class="p">()</span> <span class="ow">is</span> <span class="n">site2</span> <span class="gp">... </span> <span class="k">raise</span> <span class="ne">ValueError</span><span class="p">(</span><span class="s">'An error in the body'</span><span class="p">)</span> <span class="gt">Traceback (most recent call last):</span> <span class="c">...</span> <span class="gr">ValueError</span>: <span class="n">An error in the body</span> <span class="gp">>>> </span><span class="k">print</span> <span class="n">getSite</span><span class="p">()</span> <span class="go">None</span> </pre></div> </div> </div> </div> </div> </div> </div> <div class="sphinxsidebar"> <div class="sphinxsidebarwrapper"> <h3><a href="index.html">Table Of Contents</a></h3> <ul> <li><a class="reference internal" href="#">The current component registry</a><ul> <li><a class="reference internal" href="#context-manager">Context manager</a></li> </ul> </li> </ul> <h4>Previous topic</h4> <p class="topless"><a href="configure.html" title="previous 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