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diff --git a/app/static/doc/flask-docs/patterns/deferredcallbacks.html b/app/static/doc/flask-docs/patterns/deferredcallbacks.html new file mode 100644 index 0000000..32b6b79 --- /dev/null +++ b/app/static/doc/flask-docs/patterns/deferredcallbacks.html @@ -0,0 +1,180 @@ + +<!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>Deferred Request Callbacks — Flask 0.8 documentation</title> + + <link rel="stylesheet" href="../_static/flasky.css" type="text/css" /> + <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> + + <script type="text/javascript"> + var DOCUMENTATION_OPTIONS = { + URL_ROOT: '../', + VERSION: '0.8', + 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="Flask 0.8 documentation" href="../index.html" /> + <link rel="up" title="Patterns for Flask" href="index.html" /> + <link rel="next" title="Deployment Options" href="../deploying/index.html" /> + <link rel="prev" title="Streaming Contents" href="streaming.html" /> + + + <link rel="apple-touch-icon" href="../_static/touch-icon.png" /> + + <link media="only screen and (max-device-width: 480px)" href="../_static/small_flask.css" type= "text/css" rel="stylesheet" /> + + </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="../deploying/index.html" title="Deployment Options" + accesskey="N">next</a> |</li> + <li class="right" > + <a href="streaming.html" title="Streaming Contents" + accesskey="P">previous</a> |</li> + <li><a href="../index.html">Flask 0.8 documentation</a> »</li> + <li><a href="index.html" accesskey="U">Patterns for Flask</a> »</li> + </ul> + </div> + + <div class="document"> + <div class="documentwrapper"> + <div class="bodywrapper"> + <div class="body"> + + <div class="section" id="deferred-request-callbacks"> +<span id="deferred-callbacks"></span><h1>Deferred Request Callbacks<a class="headerlink" href="#deferred-request-callbacks" title="Permalink to this headline">¶</a></h1> +<p>One of the design principles of Flask is that response objects are created +and passed down a chain of potential callbacks that can modify them or +replace them. When the request handling starts, there is no response +object yet. It is created as necessary either by a view function or by +some other component in the system.</p> +<p>But what happens if you want to modify the response at a point where the +response does not exist yet? A common example for that would be a +before-request function that wants to set a cookie on the response object.</p> +<p>One way is to avoid the situation. Very often that is possible. For +instance you can try to move that logic into an after-request callback +instead. Sometimes however moving that code there is just not a very +pleasant experience or makes code look very awkward.</p> +<p>As an alternative possibility you can attach a bunch of callback functions +to the <a class="reference internal" href="../api.html#flask.g" title="flask.g"><tt class="xref py py-data docutils literal"><span class="pre">g</span></tt></a> object and call then at the end of the request. +This way you can defer code execution from anywhere in the application.</p> +<div class="section" id="the-decorator"> +<h2>The Decorator<a class="headerlink" href="#the-decorator" title="Permalink to this headline">¶</a></h2> +<p>The following decorator is the key. It registers a function on a list on +the <a class="reference internal" href="../api.html#flask.g" title="flask.g"><tt class="xref py py-data docutils literal"><span class="pre">g</span></tt></a> object:</p> +<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">flask</span> <span class="kn">import</span> <span class="n">g</span> + +<span class="k">def</span> <span class="nf">after_this_request</span><span class="p">(</span><span class="n">f</span><span class="p">):</span> + <span class="k">if</span> <span class="ow">not</span> <span class="nb">hasattr</span><span class="p">(</span><span class="n">g</span><span class="p">,</span> <span class="s">'after_request_callbacks'</span><span class="p">):</span> + <span class="n">g</span><span class="o">.</span><span class="n">after_request_callbacks</span> <span class="o">=</span> <span class="p">[]</span> + <span class="n">g</span><span class="o">.</span><span class="n">after_request_callbacks</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">f</span><span class="p">)</span> + <span class="k">return</span> <span class="n">f</span> +</pre></div> +</div> +</div> +<div class="section" id="calling-the-deferred"> +<h2>Calling the Deferred<a class="headerlink" href="#calling-the-deferred" title="Permalink to this headline">¶</a></h2> +<p>Now you can use the <cite>after_this_request</cite> decorator to mark a function to +be called at the end of the request. But we still need to call them. For +this the following function needs to be registered as +<a class="reference internal" href="../api.html#flask.Flask.after_request" title="flask.Flask.after_request"><tt class="xref py py-meth docutils literal"><span class="pre">after_request()</span></tt></a> callback:</p> +<div class="highlight-python"><div class="highlight"><pre><span class="nd">@app.after_request</span> +<span class="k">def</span> <span class="nf">call_after_request_callbacks</span><span class="p">(</span><span class="n">response</span><span class="p">):</span> + <span class="k">for</span> <span class="n">callback</span> <span class="ow">in</span> <span class="nb">getattr</span><span class="p">(</span><span class="n">g</span><span class="p">,</span> <span class="s">'after_request_callbacks'</span><span class="p">,</span> <span class="p">()):</span> + <span class="n">response</span> <span class="o">=</span> <span class="n">callback</span><span class="p">(</span><span class="n">response</span><span class="p">)</span> + <span class="k">return</span> <span class="n">response</span> +</pre></div> +</div> +</div> +<div class="section" id="a-practical-example"> +<h2>A Practical Example<a class="headerlink" href="#a-practical-example" title="Permalink to this headline">¶</a></h2> +<p>Now we can easily at any point in time register a function to be called at +the end of this particular request. For example you can remember the +current language of the user in a cookie in the before-request function:</p> +<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">flask</span> <span class="kn">import</span> <span class="n">request</span> + +<span class="nd">@app.before_request</span> +<span class="k">def</span> <span class="nf">detect_user_language</span><span class="p">():</span> + <span class="n">language</span> <span class="o">=</span> <span class="n">request</span><span class="o">.</span><span class="n">cookies</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s">'user_lang'</span><span class="p">)</span> + <span class="k">if</span> <span class="n">language</span> <span class="ow">is</span> <span class="bp">None</span><span class="p">:</span> + <span class="n">language</span> <span class="o">=</span> <span class="n">guess_language_from_request</span><span class="p">()</span> + <span class="nd">@after_this_request</span> + <span class="k">def</span> <span class="nf">remember_language</span><span class="p">(</span><span class="n">response</span><span class="p">):</span> + <span class="n">response</span><span class="o">.</span><span class="n">set_cookie</span><span class="p">(</span><span class="s">'user_lang'</span><span class="p">,</span> <span class="n">language</span><span class="p">)</span> + <span class="n">g</span><span class="o">.</span><span class="n">language</span> <span class="o">=</span> <span class="n">language</span> +</pre></div> +</div> +</div> +</div> + + + </div> + </div> + </div> + <div class="sphinxsidebar"> + <div class="sphinxsidebarwrapper"><p class="logo"><a href="../index.html"> + <img class="logo" src="../_static/flask.png" alt="Logo"/> +</a></p> + <h3><a href="../index.html">Table Of Contents</a></h3> + <ul> +<li><a class="reference internal" href="#">Deferred Request Callbacks</a><ul> +<li><a class="reference internal" href="#the-decorator">The Decorator</a></li> +<li><a class="reference internal" href="#calling-the-deferred">Calling the Deferred</a></li> +<li><a class="reference internal" href="#a-practical-example">A Practical Example</a></li> +</ul> +</li> +</ul> +<h3>Related Topics</h3> +<ul> + <li><a href="../index.html">Documentation overview</a><ul> + <li><a href="index.html">Patterns for Flask</a><ul> + <li>Previous: <a href="streaming.html" title="previous chapter">Streaming Contents</a></li> + <li>Next: <a href="../deploying/index.html" title="next chapter">Deployment Options</a></li> + </ul></li> + </ul></li> +</ul> + <h3>This Page</h3> + <ul class="this-page-menu"> + <li><a href="../_sources/patterns/deferredcallbacks.txt" + rel="nofollow">Show Source</a></li> + </ul> +<div id="searchbox" style="display: none"> + <h3>Quick search</h3> + <form class="search" action="../search.html" method="get"> + <input type="text" name="q" /> + <input type="submit" value="Go" /> + <input type="hidden" name="check_keywords" value="yes" /> + <input type="hidden" name="area" value="default" /> + </form> + <p class="searchtip" style="font-size: 90%"> + Enter search terms or a module, class or function name. + </p> +</div> +<script type="text/javascript">$('#searchbox').show(0);</script> + </div> + </div> + <div class="clearer"></div> + </div> + <div class="footer"> + © Copyright 2010, Armin Ronacher. + Created using <a href="http://sphinx.pocoo.org/">Sphinx</a>. + </div> + </body> +</html>
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