How can you improve code reuse and testability?

1 Use inheritance and polymorphism

One of the benefits of object oriented design is that you can use inheritance and polymorphism to create hierarchies of classes that share common attributes and behaviors, while also allowing for variations and specializations. This can help you avoid duplication of code and make your code more reusable and extensible. For example, you can define an abstract class called Animal that has properties like name, age, and weight, and methods like eat, sleep, and makeSound. Then, you can create subclasses like Dog, Cat, and Bird that inherit from Animal and override or extend some of the methods to suit their specific characteristics. This way, you can reuse the code from Animal for all the subclasses, and also use polymorphism to treat different types of animals as the same kind of object.

2 Use interfaces and abstract classes

Another way to improve code reuse and testability is to use interfaces and abstract classes to define contracts or specifications for how different classes should behave or interact. Interfaces are collections of abstract methods that a class must implement to conform to the interface. Abstract classes are classes that have some abstract methods that subclasses must override, as well as some concrete methods that can be inherited. By using interfaces and abstract classes, you can decouple your code from the implementation details of different classes and focus on the functionality and behavior. This can also make your code more testable, as you can use mock objects or stubs that implement the same interface or abstract class to simulate the behavior of real objects in your tests.

3 Use composition and delegation

Composition and delegation are two design patterns that can help you improve code reuse and testability by reducing the complexity and coupling of your classes. Composition is when a class contains one or more instances of other classes as its attributes, and uses them to provide some of its functionality. Delegation is when a class delegates some of its responsibility or behavior to another class or object, and acts as a wrapper or proxy for it. For example, you can use composition to create a class called Car that has attributes like engine, wheels, and doors, and uses them to provide methods like start, stop, and lock. You can also use delegation to create a class called RemoteControl that has an attribute called car, and delegates methods like start, stop, and lock to the car object. This way, you can reuse the functionality of existing classes without inheriting from them, and also isolate the dependencies and interactions between them.

4 Use design principles and guidelines

Finally, you can improve code reuse and testability by following some design principles and guidelines. SOLID stands for five principles that help you design cohesive, loosely coupled, and adaptable classes. DRY stands for Don't Repeat Yourself, meaning you should avoid duplication of code and logic. KISS stands for Keep It Simple, Stupid, emphasizing simplicity and clarity in your code. YAGNI stands for You Ain't Gonna Need It, which means you should focus on the current needs and requirements of your project. By applying these principles and guidelines, your code will be easier to understand, modify, and test, while also reducing the chances of errors and bugs.

5 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?