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        <h1>Refactoring Rails</h1><p>This guide will show you how to refactor
your code.  </p><p>By referring to this guide, you will be able to:</p>
<ul>
<li>Get to know some tools that help you find problematic aspects of your code</li>
<li>Learn general refactoring practice from concrete examples</li>
</ul>

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<li><a href="#refactoring">Refactoring</a></li>
<li><a href="#code-smells">Code Smells</a></li>
<li><a href="#tools-for-code-quality">Tools for Code Quality</a></li>
<li><a href="#futher-reading">Futher Reading</a></li>
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<p class='slide_break_block'><a class='slide_break' id='slide-0' href='slides_refactoring_rails.html#/0'>◻</a></p>
<h2 id="refactoring"><a class="anchorlink" href="#refactoring"><span>1</span> Refactoring</a></h2><p>Never be ashamed of making you code better.  On the contrary: recognizing code smells
in your old code means that you learnt something in the meantime.
Only very inexperienced people think that the code they wrote yesterday is
perfect.</p><p>Refactoring is </p>
<ul>
<li>restructuring an existing body of code</li>
<li>altering its internal structure</li>
<li>without changing its external behavior <a href="https://en.wikipedia.org/wiki/Refactoring">wikipedia</a></li>
</ul>
<p>We will use <strong>tests</strong> to ensure that we do not change the external behavior
of the code we are refactoring.</p><p>A <strong>code smell</strong> is a piece of bad code that we recognize.</p><p>Read the Ruby version of Fowlers refactoring book to
learn both code smells and refactorings:</p></div>
<div class='slide'>
<p class='slide_break_block'><a class='slide_break' id='slide-1' href='slides_refactoring_rails.html#/1'>◻</a></p>
<h2 id="code-smells"><a class="anchorlink" href="#code-smells"><span>2</span> Code Smells</a></h2><p>This is the list of code smells from
Fields, Harvie, Fowler(2010): Refactoring, Ruby Edition. Addison-Wesley.
In chapter 6 to 12 of that book they describe refactorings to handle
all these problems and more:</p>
<ul>
<li>Duplicated Code</li>
<li>Long Method</li>
<li>Large Class</li>
<li>Long Parameter List</li>
<li>Divergent Change</li>
<li>Shotgun Surgery</li>
<li>Feature Envy.</li>
<li>Data Clumps.</li>
<li>Primitive Obsession</li>
<li>Case Statements</li>
<li>Parallel Inheritance Hierarchies</li>
<li>Lazy Class.</li>
<li>Speculative Generality.</li>
<li>Temporary Field</li>
<li>Message Chains</li>
<li>Middle Man</li>
<li>Inappropriate Intimacy</li>
<li>Alternative Classes with Different Interfaces.</li>
<li>Incomplete Library Class</li>
<li>Data Class</li>
<li>Refused Bequest</li>
<li>Comments</li>
<li>Metaprogramming Madness</li>
<li>Disjointed API</li>
<li>Repetitive Boilerplate</li>
</ul>
</div>
<div class='slide'>
<p class='slide_break_block'><a class='slide_break' id='slide-2' href='slides_refactoring_rails.html#/2'>◻</a></p>
<h2 id="tools-for-code-quality"><a class="anchorlink" href="#tools-for-code-quality"><span>3</span> Tools for Code Quality</a></h2><p>Recognizing code that is problematic and should be refactored
is one of the main skills of a developer.  Often it is not a
black and white situation: there might be several ways of writing
a certain piece of code, each with it's own pros and cons.<br>
A tool cannot help you make these decision.</p><p>But there is a role for tools in this process: especially when
faced with a lot of code there are tools that can help
you find places you should look at.</p><p>A <a href="https://en.wikipedia.org/wiki/Software_metric">code metric</a> is
a quantitive measure of the quality of a piece of code.</p><p>The Gem <code>metric_fu</code> combines some metrics. Install it in your
Gemfile, and add a task-file, and run it on the command line <code>metriy_fu</code>.
It will generate a report in <code>tmp/metric_fu/output/</code>. </p><p><strong>Saikuro</strong> is a good place to start reading the report: it
measures  cyclomatic complexity, or how deep you nest your control structures.</p><p>See <a href="http://railscasts.com/episodes/166-metric-fu?view=asciicast">Rails Cast no
166</a> for a more
detailed introduction to metric_fu.</p><p>Another tool to help find spots where you can improve the quality of
your code is <code>rails_best_practices</code>.  Install the gem, but don't put
it in your <code>Gemfile</code>.  Just run <code>rails_best_practices -f html</code> in
the main directory of your app.  The result will be written to
<code>./rails_best_practices_output.html</code>.</p></div>
<div class='slide'>
<p class='slide_break_block'><a class='slide_break' id='slide-3' href='slides_refactoring_rails.html#/3'>◻</a></p>
<h2 id="futher-reading"><a class="anchorlink" href="#futher-reading"><span>4</span> Futher Reading</a></h2>
<ul>
<li>Fowler, Beck, Brant, Opdyke, Roberts(1999). Refactoring: improving the design of existing code. Addison Wesley. ISBN: 0-201-48567-2.</li>
<li>Fields, Harvie, Fowler(2010): Refactoring, Ruby Edition. Addison-Wesley.</li>
<li><a href="https://github.com/facebook/codemod">codemod</a> a python script</li>
</ul>
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        <p class="copyright">published under <a href="https://creativecommons.org/licenses/by-nc-sa/3.0/at/deed.de">creative commons by-nc-sa</a> in 2012-2025 by <a href="https://brigitte-jellinek.at">Brigitte Jellinek</a>.
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