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115 lines
4.1 KiB
115 lines
4.1 KiB
11 months ago
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta http-equiv="X-UA-Compatible" content="IE=edge">
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<meta http-equiv="content-type" content="text/html; charset=utf-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1, viewport-fit=cover">
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<title>Julio Biason .Me 4.3</title>
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<link rel="stylesheet" href="https://blog.juliobiason.me/print.css" media="print">
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</head>
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<body class=" ">
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<div class="sidebar">
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<div class="container sidebar-sticky">
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<div class="sidebar-about">
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<a href="https://blog.juliobiason.me"><h1>Julio Biason .Me 4.3</h1></a>
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<p class="lead">Old school dev living in a 2.0 dev world</p>
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</div>
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<ul class="sidebar-nav">
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<li class="sidebar-nav-item"><a href="/">English</a></li>
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<li class="sidebar-nav-item"><a href="/pt">Português</a></li>
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<li class="sidebar-nav-item"><a href="/tags">Tags (EN)</a></li>
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<li class="sidebar-nav-item"><a href="/pt/tags">Tags (PT)</a></li>
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</ul>
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<div class="content container">
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<div class="post">
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<h1 class="post-title">Things I Learnt The Hard Way - Don't Use Booleans As Parameters</h1>
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<span class="post-date">
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2019-06-23
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<a href="https://blog.juliobiason.me/tags/books/">#books</a>
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<a href="https://blog.juliobiason.me/tags/things-i-learnt/">#things i learnt</a>
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<a href="https://blog.juliobiason.me/tags/booleans/">#booleans</a>
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<a href="https://blog.juliobiason.me/tags/functions/">#functions</a>
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<a href="https://blog.juliobiason.me/tags/parameters/">#parameters</a>
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</span>
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<p>When you're designing a function, you may be tempted to add a flag (a
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parameter in a function that it is a boolean). Don't do this.</p>
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<span id="continue-reading"></span>
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<p>Here, let me show you an example: Suppose you have a messaging system and you
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have a function that returns all the messages to an user, called
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<code>getUserMessages</code>. But there is a case where you need to return a summary of
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each message (say, the first paragraph) or the full message. So you add a
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flag/Boolean parameter called <code>retrieveFullMessage</code>.</p>
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<p>Again, don't do that.</p>
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<p>'Cause anyone reading your code will see <code>getUserMessage(userId, true)</code> and
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wonder what the heck that <code>true</code> means.</p>
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<p>You can either rename the function to <code>getUserMessageSummaries</code> and have
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another <code>getUserMessagesFull</code> or something around those lines, but each
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function just call the original <code>getUserMessage</code> with true or false -- but the
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interface to the outside of your class/module will still be clear.</p>
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<p>But <em>don't</em> add flags/Boolean parameters to your API.</p>
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<div>
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<div style="float:left">
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<< <a href="/books/things-i-learnt/future-trashing">Future Thinking is Future Trashing</a>
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</div>
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<div style="float:right">
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<a href="/books/things-i-learnt/interface-changes">Beware of Interface Changes</a> >>
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</div>
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</div>
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</div>
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</body>
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</html>
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