10 Software Design Patterns Made Simple: A Guide for New Programmers

When you start out as a new programmer, your code might be messy - like snakes made of Play-Doh. As you grow into a senior developer, you learn to make your code beautiful and organized - like a masterpiece. But interestingly, when you become a principal engineer with years of experience, you often go back to simpler solutions - back to those Play-Doh snakes - because they're easier to maintain!

In this post, we'll look at 10 common system design patterns that can help you write better code. These patterns are like recipes that solve common programming problems.

What Is a Software Design Pattern?

Software design patterns are proven solutions to problems that programmers face over and over again. They come from a famous book written by four programmers (nicknamed "The Gang of Four") that describes 23 different patterns.

These patterns fall into three main groups:

• Creational patterns: How objects are created

• Structural patterns: How objects relate to each other

• Behavioral patterns: How objects talk to each other

Remember: Being a good programmer isn't about memorizing code - it's about solving problems. Design patterns in programming are tools to help you solve those problems efficiently.

Singleton Pattern

The Singleton pattern ensures that a class can only have one object created from it. It's like having only one president of a country at a time.

How it works:

• Make it impossible to create new objects directly

• Create a special method that checks if an object already exists

• If no object exists, create one; if one already exists, return that one

When to use it: This is good for things like app settings, where you only want one set of settings across your entire program. The singleton design pattern is one of the most important design patterns for interviews and is widely used in system design patterns.

Worth noting: In JavaScript, you can often just use a regular object instead of this pattern. Don't use fancy patterns when simple solutions work!

Prototype Pattern

The Prototype pattern is all about cloning objects. Instead of creating new objects from scratch, you make copies of existing ones.

How it works:

• Start with a base object (the prototype)

• Create new objects by copying the prototype and adding or changing what you need

When to use it: This is useful when creating new objects from scratch is expensive or complicated. JavaScript actually has this built in! If you're wondering "What is an example of a prototype?" consider object cloning in JavaScript or deep-copying objects in various programming languages.

Builder Pattern

Imagine ordering a hot dog with all your favorite toppings. Instead of giving all those details at once, the Builder pattern lets you add them step-by-step.

How it works:

• Create an object with a basic structure

• Add methods that let you set different properties one by one

• Each method returns the object itself so you can chain methods together

When to use it: This is helpful when creating complex objects with many optional parts. If you've ever asked, "What is the builder pattern?" it's a structured way to construct objects step-by-step. The builder pattern is one of the most commonly used system design patterns.

Factory Pattern

The Factory design pattern lets you create objects without specifying the exact class of object you want to create.

How it works:

• Create a factory function or class

• The factory decides which specific type of object to create based on certain conditions

• Return the created object

When to use it: This is great for cross-platform apps where you need different objects based on the platform (like iOS vs Android buttons). If you're wondering "What is the factory pattern?" or "How to design a factory?", this pattern provides a flexible way to create objects.

Facade Pattern

A facade is like the front of a building - it hides all the complexity inside. This pattern provides a simple interface to a complex system.

How it works:

• Create a new class that simplifies how you work with complex systems

• Hide all the messy details behind this simple interface

When to use it: Use this when you want to make a complicated system easier to use. Many JavaScript libraries are facades! The facade pattern is useful in software architectures where abstraction improves usability.

Proxy Pattern

A proxy is a stand-in for something else - like a substitute teacher. It looks and acts like the original but can do extra things.

How it works:

• Create an object that has the same methods as the original

• This new object forwards calls to the original object

• The proxy can add extra behavior before or after forwarding the call

When to use it: This is used in frameworks like Vue.js to track when data changes so they can update the screen automatically. If you’re wondering "Why is proxy used?", it helps manage access to objects and adds additional functionalities like security or logging.

Iterator Pattern

The Iterator pattern helps you move through a collection of objects one by one without having to know how the collection is structured.

How it works:

• Create a system that keeps track of the current position in a collection

• Provide methods to get the current item and move to the next one

• Tell when you've reached the end

When to use it: This is built into many programming languages. In JavaScript, it's what makes for...of loops work! The iterator pattern is an essential pattern to understand "What is iteration in design?".

Observer Pattern

The Observer pattern lets objects watch for changes in other objects. It's like subscribing to a YouTube channel - you get notified when there's new content.

How it works:

• One object (the subject) maintains a list of dependents (observers)

• When the subject changes, it notifies all observers

• Each observer then does something in response

When to use it: This is common in apps where changes in one place should cause updates elsewhere, like when database changes need to update multiple screens. The observer pattern is commonly used in event-driven architectures.

Mediator Pattern

The Mediator pattern is like an air traffic controller - instead of having planes talk directly to each other, they all talk through the controller.

How it works:

• Create a mediator object

• Instead of objects communicating directly, they go through the mediator

• The mediator coordinates all the communication

When to use it: This is helpful when you have many objects that need to work together, but direct communication would be too complex.

State Pattern

The State pattern changes how an object behaves based on its internal state. It's like how people act differently when they're happy versus when they're sad.

How it works:

• Create a separate class for each possible state

• Each state class implements the same methods but behaves differently

• The main object delegates to its current state

When to use it: This is useful when an object needs to change its behavior completely based on some internal condition. The state design pattern in Java is commonly used in workflows and game development.

Final Thoughts

Design patterns are powerful tools, but they aren't always necessary. Sometimes simple solutions work best. As the old saying goes: "Make things as simple as possible, but not simpler."

Remember that as a programmer, your job is to solve problems - use these patterns when they help, but don't force them where they don't fit.

What design patterns have you found most useful in your coding? Share your experiences in the comments