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114 lines
4.1 KiB
114 lines
4.1 KiB
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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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<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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<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 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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<a href="/books/things-i-learnt/interface-changes">Beware of Interface Changes</a> >> |
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