Just because it’s not an error doesn’t mean it’s right

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I was working on a PHP script the other day, and the damn bastard just wouldn’t work. I mean, the code was fine, no errors, no problems in compilation or anything like that. It ran perfectly, except that it didn’t do what I wanted. Worse than that: it was inconsistent about it, sometimes it was fine, and sometimes the results just didn’t make sense. It all depended on the input it got.

After much head scratching and dark thoughts about throwing my computer out the window and becoming a Shepperd, I found the problem: in one of the functions that was suppose to cleanse the input had a call to strripos when it really needed a call to strrpos, happens.

The thing is that this really shouldn’t happen, and if it does it shouldn’t take so long to diagnose. What a function does should be immediately and unambiguously clear by looking at its name. when you have strripos and strrpos, strtr and strstr, and stripslashes and stripcslashes, that makes it very hard to understand the code. I consider this readability problem to be one of the most fundamental flaws of PHP as a language. Luckily, this was a fairly simple and easily tested script. But consider having to read through 10,000 lines of code just to figure this out. (Yes, I know, you wouldn’t actually read all the code, you’d debug and trace the problem. But the point still stands that the code is harder to read)

Java, thankfully, does not do this. The naming conventions in Java describe ways to avoid this kind of scenario by outlining method names like “toString” “getVariable” and “isValid” which are self-explanatory. But this does not mean that Java is innocent of sin. Consider this scenario: You have a class MyClass and you need to write two constructors for it. Each constructor gets a JFrame and a String, and based on which ones it gets, it will show different information in the frame.

Now, since these are constructors, you can’t give them different names. And since they both have the same number and types of variables, you can’t distinguish them that way. So what you end up doing is distinguishing between them based on the variable order: One constructor is going to be MyClass (String, JFrame) and the other will be MyClass(JFrame, String). All perfectly legal in Java and aren’t you smart.

But now you face the same problem that I faced earlier in PHP: your method calls are non-descriptive and you can’t, based on the method name and signature, tell which constructor your actually using. Sure, you remember which is which now, but what about in six months when you have to get back to it and you’ve forgotten it all, or worse, someone has to maintain your code?

There are several solutions to avoid this kind of problem. My personal favorite is the one suggested by Joshua Bloch in his book “Effective Java” where he recommends using static factory methods instead of constructors.  Consider the two constructors above: If you made them private and instead added static methods with distinct names static getNewMyClassA and static getNewMyClassB you would eliminate the confusion and make it unambiguously clear as to which method does what. Furthermore, you’d gain much greater control over your Object creation, allowing your class to offer objects out of a pool, for example, rather than creating a new object every time. You also have a polymorphic advantage: a static method can return an object of any subclass of its return type, which can be handy.

Debugging and maintaining code are some of the most challenging tasks that a programmer can face. Sometimes, making the code more readable can be the only thing between you and a life as a walking sheepdog. 🙂



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