THE ART OF REFACTORING ENHANCING CODE QUALITY AND MAINTAINABILITY Prepared By: Asmit Ghimire

Introduction ➔ Refactoring is the process of restructuring code while not changing its original functionality. ➔ The main purpose of refactoring is to enhance the code's readability, maintainability, and overall quality, making it easier to understand and modify while reducing technical debt.

Why Refactoring Matters ➔ Improved code quality / readability ➔ Maintainability ➔ Reduced technical debt ➔ Quicker issue diagnosis ➔ Enhanced team collaboration ➔ Improved extensibility ➔ Performance gain in some cases

Signs It's Time to Refactor ➔ Code Duplication ➔ Long Methods / Functions ➔ Complex Conditional Statements ➔ Tight Coupling ➔ Performance Issues ➔ Changing Requirements ➔ Excessive Comments

Refactoring Techniques ➔ Descriptive names to variables, methods, and classes ➔ Replace Magic Numbers with Named Constants ➔ Consolidate Conditional Expressions ➔ Introduce Explaining Variable ➔ Introduce Parameter Object ➔ Remove Dead Code ➔ Separate Concerns with Design Patterns ➔ Pull Up / Push Down Methods ➔ Replace Conditional with Polymorphism

Pull Up Method ➔ Problem ◆ Your subclasses have methods that perform similar work. ➔ Solution ◆ Make the methods identical and then move them to the relevant superclass.

Push Down Method ➔ Problem ◆ Is behavior implemented in a superclass used by only one (or a few) subclasses? ➔ Solution ◆ Move this behavior to the subclasses.

Replace Conditionals with Polymorphism ➔ Problem ◆ You have a conditional that performs various actions depending on object type or properties. class Bird { // ... public function getSpeed() { switch ($this->type) { case EUROPEAN: return $this->getBaseSpeed(); case AFRICAN: return $this->getBaseSpeed() - $this->getLoadFactor() * $this->numberOfCoconuts; case NORWEGIAN_BLUE: return ($this->isNailed) ? 0 : $this->getBaseSpeed($this->voltage); } throw new Exception("Should be unreachable" ); } // ... }

Replace Conditionals with Polymorphism ➔ Solution ◆ Create subclasses matching the branches of the conditional. ◆ In them, create a shared method and move code from the corresponding branch of the conditional to it. ◆ Then replace the conditional with the relevant method call. abstract class Bird { // ... abstract function getSpeed(); // ... } class European extends Bird { public function getSpeed() { return $this->getBaseSpeed(); } } class African extends Bird { public function getSpeed() { return $this->getBaseSpeed() - $this->getLoadFactor() * $this->numberOfCoconuts; } } class NorwegianBlue extends Bird { public function getSpeed() { return ($this->isNailed) ? 0 : $this->getBaseSpeed($this->voltage); } } // Somewhere in Client code. $speed = $bird->getSpeed();

Steps to Successful Refactoring ➔ Identify the target area for refactoring. ➔ Understand the existing behavior and write tests. ➔ Apply the chosen refactoring technique. ➔ Run tests to verify correctness. ➔ Commit changes to version control.

Tools and Resources ➔ SonarQube: Provides extensive static code analysis, detecting bugs, vulnerabilities, and code smells across multiple languages. ➔ CodeClimate: Analyzes code quality, security, and maintainability, offering insights and metrics.

Challenges ➔ Time and Resources ➔ Risk of Introducing Bugs ➔ Lack of Automated Tests ➔ Legacy Code and Dependencies ➔ Team Buy-In ➔ Scope Creep ➔ Balancing Refactoring with New Features ➔ Resistance to Change ➔

“Code refactoring is like doing the dishes: it's not fun, but leaving them all piled up will make things worse.”

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