Anti patterns in software

Good software structure is essential for system extension and maintenance. Software development is a chaotic activity, therefore the implemented structure of systems tends to stray from the planned structure as determined by architecture, analysis, and design. The structure changes because programmers learn constraints and approaches that alter the context of the coded solutions. When used properly, refactoring is a natural activity in the programming process.

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This cookie contains partner user IDs and last successful match time. It can also limit the usefulness of refactoring and code analysis tools. Learn to use the platform or features provided by your OS or platform instead.

Avoid the temptation to create language constructs that rival existing constructs especially if it's because you are not used to a new language and miss your old language's features. Using your MySQL database as a job queue. Reimplementing your own disk buffer cache mechanism instead of relying on your OS's. Writing a task scheduler for your web-server in PHP. Defining macros in C to allow for Python-like language constructs.

In very rare cases, it might be necessary re-implement parts of the platform JVM, Firefox, Chrome, etc. The main problem is that the semantics of the number or string literal is partially or completely hidden without a descriptive name or another form of annotation. This makes understanding the code harder, and if it becomes necessary to change the constant, search and replace or other refactoring tools can introduce subtle bugs. Consider the following piece of code:.

What are the two numbers there? Assume the first is window width and the second in window height. If it ever becomes necessary to change the width to instead, a search and replace would be dangerous since it would change the height in this case too, and perhaps other occurrences of the number in the code base.

String literals might seem less prone to these issues but having unnamed string literals in code makes internationalization harder, and can introduce similar issues to do with instances of the same literal having different semantics. For example, homonyms in English can cause a similar issue with search and replace; consider two occurrences of "point", one in which it refers to a noun as in "she has a point" and the other as a verb as in "to point out the differences Replacing such string literals with a string retrieval mechanism that allows you to clearly indicate the semantics can help distinguish these two cases, and will also come in handy when you send the strings for translation.

Simple example is shown above. This particular anti-pattern is very easy to detect except for a few tricky cases mentioned below. There is a narrow grey area where it can be hard to tell if certain numbers are magic numbers or not. For example the number 0 for languages with zero-based indexing. Other examples are use of to calculate percentages, 2 to check for parity, etc.

Numbers are great. However, blind reliance on numbers can be dangerous. For example, numbers tend to outlive the models in which they were meaningful, or the models become outdated and no longer accurately represent reality. Grade inflation is an example of this.

Source in Polish , and the the Reddit post that I first saw this in. Using only lines of code, number of commits, etc. Measuring employee contribution by the numbers of hours they spend at their desks.

The larger the scale of operations, the higher the number of decisions that will need to be made, and this means automation and blind reliance on numbers for decisions begins to creep into the processes. Useless classes with no real responsibility of their own, often used to just invoke methods in another class or add an unneeded layer of abstraction.

Poltergeist classes add complexity, extra code to maintain and test, and make the code less readable—the reader first needs to realize what the poltergeist does, which is often almost nothing, and then train herself to mentally replace uses of the poltergeist with the class that actually handles the responsibility.

Don't write useless classes, or refactor to get rid of them. Jack Diederich has a great talk titled Stop Writing Classes that is related to this anti-pattern. A couple of years ago, while working on my master's degree, I was a teaching assistant for a first-year Java programming course. For one of the labs, I was given the lab material which was to be on the topic of stacks and using linked lists to implement them.

I was also given the reference "solution". This is the solution Java file I was given, almost verbatim I removed the comments to save some space :. You can only imagine my confusion looking at the reference solution, trying to figure what the point of the LabStack class was, and what the students were supposed to learn from the utterly pointless exercise of writing it.

In case it's not painfully obvious what's wrong with the class, it's that it does absolutely nothing! In our room addition example, a hammer is a very useful tool, but would you try to use it to saw a piece of wood? A boat anchor anti-pattern happens when somebody leaves a piece of code in the codebase not because it belongs there but because it might be needed later. The reasoning is that when the code is needed later, it will be easy to turn it on and get it running.

Like a boat anchor, this type of anti-pattern weighs down your project and can keep it from moving forward quickly. All this extra, unneeded code bloats the codebase and slows down your build times. And if you inadvertently turn on one or more of these boat anchor anti-patterns, it could cause problems such as breaking the build and adding technical risk or debt. The code is unnecessary and wastes processing resources.

For example, many years ago a technical writer was working on documenting solutions for error codes thrown from networking software. The code was essentially dead and needed to be removed. But the engineers were reluctant to remove it because they were afraid it would introduce new bugs or break the code.

Dead code anti-patterns are heavy, do nothing for the program, slow down development, increase build times, and are difficult to maintain. When you have an object or class that is doing too much and is responsible for too many things, it might be considered a God object. Assigning too much responsibility goes against the single responsibility principle of object-oriented design. For example, a customer ID object that is responsible for the user ID, first name, last name, list of items to purchase, total amount spent, transaction ID, and so on, might be a God object.