Bad Smells in Code

Mysterious Name

If you can't tell what a function, variable, or class does from its name, that's a smell. Good names are the most important tool for clear code. Renaming is one of the most common and most valuable refactorings. If you struggle to name something, it's often a sign the design is unclear.

Duplicated Code

The same code structure in more than one place. Extract the duplication into a single function. If the duplication is in sibling classes, pull it up into the parent. Duplication means every change needs to happen in multiple places — and you will forget one.

Long Function

The longer a function, the harder it is to understand. Small functions with good names are self-documenting. The key isn't a line count — it's whether you need a comment to explain a block. If yes, extract that block into a function and name it after the comment.

Conditionals and loops are prime extraction candidates. A function should do one thing at one level of abstraction.

Feature Envy

A function that spends more time interacting with another class's data than with its own. If calculateTotal mostly accesses fields on Order, it probably belongs on Order. Move it. The goal is to keep data and the behavior that uses it together.

Related smells: data clumps (groups of data that always appear together should be their own object), long parameter lists (often a sign that a function is reaching into too many concerns), shotgun surgery (one change requires edits across many classes).