Programming is both an art and a science. While creativity is essential, established standards and general patterns make writing code easier. Design patterns are templates for object-oriented code that allow you to spend mental energy on functionality rather than implementation. You do not need to memorize them all, but familiarity with the 23 standard design patterns will serve you well.

What Are Design Patterns?

According to Wikipedia:

general, reusable solution to a commonly occurring problem within a given context in software design

Design patterns give you proven solutions to common problems. However, be wary of viewing every engineering problem through the lens of design patterns. They are solutions to problems, not something you shoehorn into every codebase. With familiarity and time, you will naturally see problems best solved with a design pattern.

Creational

Creational design patterns let you abstract away the creation of an object. They are helpful when object creation relies on complex logic or many parameters/attributes.

Behavioral

Behavioral design patterns deal with algorithms -- behavior -- and let you abstract them away.

Structural

Structural design patterns concern defining relationships between classes and objects. The relationships allow composing smaller classes and objects into bigger ones.

Why Use Them?

The purpose of design patterns is two-fold: to make your code more reusable and to save mental energy for other aspects of writing code.

Reusability

At the heart of every design pattern is reusability and extensibility. They are strategies to flexibly accomplish tasks that can be modified in a logical and consistent way. For example, the Abstract Factory can easily be extended by adding one more class that implements the factory interface. The Strategy Pattern can be extended by adding more algorithms that implement the strategy interface. Often, extending code that uses a design pattern is as simple as adding another implementation of an interface.

Don't Reinvent The Wheel

Design patterns are just that - patterns. They are templates that we can follow to accomplish tasks. Following a pattern saves us the mental energy of devising a maintainable and usable solution and allows us to spend energy on using the solution to solve problems.

Resources to Learn Design Patterns

• Design Patterns: Elements of Reusable Object-Oriented Software - book
• Design Patterns for Humans - GitHub

Takeaway

Design patterns provide proven methods to solve common problems faced in software engineering. They promote maintainable and reusable object-oriented codebases. However, be wary of trying to solve every problem with a design pattern. They are tools, and you should pick the right tool for the job.