1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
|
<!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>Application Factories — 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="Application Dispatching" href="appdispatch.html" />
<link rel="prev" title="Larger Applications" href="packages.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="appdispatch.html" title="Application Dispatching"
accesskey="N">next</a> |</li>
<li class="right" >
<a href="packages.html" title="Larger Applications"
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="application-factories">
<span id="app-factories"></span><h1>Application Factories<a class="headerlink" href="#application-factories" title="Permalink to this headline">¶</a></h1>
<p>If you are already using packages and blueprints for your application
(<a class="reference internal" href="../blueprints.html#blueprints"><em>Modular Applications with Blueprints</em></a>) there are a couple of really nice ways to further improve
the experience. A common pattern is creating the application object when
the blueprint is imported. But if you move the creation of this object,
into a function, you can then create multiple instances of this and later.</p>
<p>So why would you want to do this?</p>
<ol class="arabic simple">
<li>Testing. You can have instances of the application with different
settings to test every case.</li>
<li>Multiple instances. Imagine you want to run different versions of the
same application. Of course you could have multiple instances with
different configs set up in your webserver, but if you use factories,
you can have multiple instances of the same application running in the
same application process which can be handy.</li>
</ol>
<p>So how would you then actually implement that?</p>
<div class="section" id="basic-factories">
<h2>Basic Factories<a class="headerlink" href="#basic-factories" title="Permalink to this headline">¶</a></h2>
<p>The idea is to set up the application in a function. Like this:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">def</span> <span class="nf">create_app</span><span class="p">(</span><span class="n">config_filename</span><span class="p">):</span>
<span class="n">app</span> <span class="o">=</span> <span class="n">Flask</span><span class="p">(</span><span class="n">__name__</span><span class="p">)</span>
<span class="n">app</span><span class="o">.</span><span class="n">config</span><span class="o">.</span><span class="n">from_pyfile</span><span class="p">(</span><span class="n">config_filename</span><span class="p">)</span>
<span class="kn">from</span> <span class="nn">yourapplication.views.admin</span> <span class="kn">import</span> <span class="n">admin</span>
<span class="kn">from</span> <span class="nn">yourapplication.views.frontend</span> <span class="kn">import</span> <span class="n">frontend</span>
<span class="n">app</span><span class="o">.</span><span class="n">register_blueprint</span><span class="p">(</span><span class="n">admin</span><span class="p">)</span>
<span class="n">app</span><span class="o">.</span><span class="n">register_blueprint</span><span class="p">(</span><span class="n">frontend</span><span class="p">)</span>
<span class="k">return</span> <span class="n">app</span>
</pre></div>
</div>
<p>The downside is that you cannot use the application object in the blueprints
at import time. You can however use it from within a request. How do you
get access to the application with the config? Use
<a class="reference internal" href="../api.html#flask.current_app" title="flask.current_app"><tt class="xref py py-data docutils literal"><span class="pre">current_app</span></tt></a>:</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">current_app</span><span class="p">,</span> <span class="n">Blueprint</span><span class="p">,</span> <span class="n">render_template</span>
<span class="n">admin</span> <span class="o">=</span> <span class="n">Blueprint</span><span class="p">(</span><span class="s">'admin'</span><span class="p">,</span> <span class="n">__name__</span><span class="p">,</span> <span class="n">url_prefix</span><span class="o">=</span><span class="s">'/admin'</span><span class="p">)</span>
<span class="nd">@admin.route</span><span class="p">(</span><span class="s">'/'</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">index</span><span class="p">():</span>
<span class="k">return</span> <span class="n">render_template</span><span class="p">(</span><span class="n">current_app</span><span class="o">.</span><span class="n">config</span><span class="p">[</span><span class="s">'INDEX_TEMPLATE'</span><span class="p">])</span>
</pre></div>
</div>
<p>Here we look up the name of a template in the config.</p>
</div>
<div class="section" id="using-applications">
<h2>Using Applications<a class="headerlink" href="#using-applications" title="Permalink to this headline">¶</a></h2>
<p>So to use such an application you then have to create the application
first. Here an example <cite>run.py</cite> file that runs such an application:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">yourapplication</span> <span class="kn">import</span> <span class="n">create_app</span>
<span class="n">app</span> <span class="o">=</span> <span class="n">create_app</span><span class="p">(</span><span class="s">'/path/to/config.cfg'</span><span class="p">)</span>
<span class="n">app</span><span class="o">.</span><span class="n">run</span><span class="p">()</span>
</pre></div>
</div>
</div>
<div class="section" id="factory-improvements">
<h2>Factory Improvements<a class="headerlink" href="#factory-improvements" title="Permalink to this headline">¶</a></h2>
<p>The factory function from above is not very clever so far, you can improve
it. The following changes are straightforward and possible:</p>
<ol class="arabic simple">
<li>make it possible to pass in configuration values for unittests so that
you don’t have to create config files on the filesystem</li>
<li>call a function from a blueprint when the application is setting up so
that you have a place to modify attributes of the application (like
hooking in before / after request handlers etc.)</li>
<li>Add in WSGI middlewares when the application is creating if necessary.</li>
</ol>
</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="#">Application Factories</a><ul>
<li><a class="reference internal" href="#basic-factories">Basic Factories</a></li>
<li><a class="reference internal" href="#using-applications">Using Applications</a></li>
<li><a class="reference internal" href="#factory-improvements">Factory Improvements</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="packages.html" title="previous chapter">Larger Applications</a></li>
<li>Next: <a href="appdispatch.html" title="next chapter">Application Dispatching</a></li>
</ul></li>
</ul></li>
</ul>
<h3>This Page</h3>
<ul class="this-page-menu">
<li><a href="../_sources/patterns/appfactories.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>
|
