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HomeBlogWeb Development10 Best Software Design Patterns in 2024 [Types & Benefits]
In software development using object-oriented programming (OOPS) we face many common problems while writing code. When similar problems are solved in similar ways while writing the code, the solution derived is given a name and explained in detail. That is how a pattern is discovered. Therefore, Design Patterns in Software Design are typical solutions to such problems.
Before we dig deep into What are Software Design Patterns? I would encourage you to know the History of Patterns. There is a book called “A Pattern Language: Towns, Buildings, Construction” authored by Christopher Alexander in which he was the first one to describe the concept of patterns.
This concept of patterns was picked up by four authors namely Erich Gamma, John Vlissides, Ralph Johnson, and Richard Helm. They applied the idea of patterns to programming and authored the book “Design Patterns: Elements of Reusable Object-Oriented Software”. This name was then shortened to “the GoF book” (the Gang of Four book). This book featured 23 patterns in design patterns which were used to solve problems related to object-oriented design.
A Software Design Pattern is a tried and tested, reusable solution to a common problem in software development. It provides a very structured approach to addressing specific design challenges which promotes efficiency, reliability, and maintainability in software systems. Most people get confused between Algorithms and Patterns because both provide solutions to commonly recurring problems.
Let’s consider this analogy to differentiate between an Algorithm and a Software Design Pattern. Suppose you are preparing a very delicious blueberry cheesecake for dessert. The Algorithm will give you clear steps on how to prepare the cheesecake whereas the Software Design Pattern will tell you the characteristics and the result which is a cheesecake, and it is on you how to prepare and bake it.
Let me unveil a bitter truth to the readers; there are many programmers in the IT Industry who wouldn’t have even heard or known about Software Design Patterns and Principles, and they even would be implementing many of them without even knowing about it. So, why is there a need to learn Software Design Patterns?
This is why mastering Software Design Patterns is very crucial for any aspiring developer. We will be talking about Software Design Pattern examples later in this article. You can take your development skills to the next level by enrolling for our Software Engineering online certificate programs.
Software Design Patterns are categorized into three types namely -
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Below are the Creational patterns in Design Patterns -
Below are the Structural patterns in Design Patterns -
Below are the Behavioral patterns in Design Patterns -
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The most popular Software Design Patterns are as follows -
This is how you implement a Singleton Design Pattern -
using System; public sealed class Singleton { private Singleton() {} private static Singleton _instance; public static Singleton GetInstance() { if (_instance == null) { _instance = new Singleton(); } return _instance; } } class Program { static void Main(string[] args) { Singleton singleton = Singleton.GetInstance(); Singleton anotherInstance = Singleton.GetInstance(); Console.WriteLine("Are both instances the same? " + (singleton == anotherInstance)); } }
This is how you implement a Prototype Design Pattern -
using System; public interface ICloneableShape { ICloneableShape Clone(); } public class Circle : ICloneableShape { private int radius; public Circle(int radius) { this.radius = radius; } public ICloneableShape Clone() { return new Circle(this.radius); } } class Program { static void Main(string[] args) { Circle circlePrototype = new Circle(7); Circle clonedCircle = (Circle)circlePrototype.Clone(); } }
This is how you implement a Facade Design Pattern -
using System; class SubsystemA { public void OperationA() { Console.WriteLine("Subsystem A: Operation A"); } } class SubsystemB { public void OperationB() { Console.WriteLine("Subsystem B: Operation B"); } } class Facade { private SubsystemA subsystemA; private SubsystemB subsystemB; public Facade() { subsystemA = new SubsystemA(); subsystemB = new SubsystemB(); } public void PerformOperation() { subsystemA.OperationA(); subsystemB.OperationB(); } } class Program { static void Main(string[] args) { Facade facade = new Facade(); facade.PerformOperation(); } }
This is how you implement a Strategy Design Pattern -
using System; public class ConcreteStrategyA { public void Execute() { Console.WriteLine("Executing strategy A"); } } public class ConcreteStrategyB { public void Execute() { Console.WriteLine("Executing strategy B"); } } public class Context { private dynamic strategy; public void SetStrategy(dynamic strategy) { this.strategy = strategy; } public void ExecuteStrategy() { strategy.Execute(); } } class Program { static void Main(string[] args) { Context context = new Context(); context.SetStrategy(new ConcreteStrategyA()); context.ExecuteStrategy(); context.SetStrategy(new ConcreteStrategyB()); context.ExecuteStrategy(); } }
This is how you implement an Observer Design Pattern -
using System; using System.Collections.Generic; public class ConcreteSubject { private List < ConcreteObserver > observers = new List < ConcreteObserver > (); public void RegisterObserver(ConcreteObserver observer) => observers.Add(observer); public void NotifyObservers(string message) => observers.ForEach(o => o.Update(message)); } public class ConcreteObserver { private string name; public ConcreteObserver(string name) => this.name = name; public void Update(string message) => Console.WriteLine($"{name} received message: {message}"); } class Program { static void Main(string[] args) { ConcreteSubject subject = new ConcreteSubject(); subject.RegisterObserver(new ConcreteObserver("Observer 1")); subject.RegisterObserver(new ConcreteObserver("Observer 2")); subject.NotifyObservers("Hello, observers!"); } }
This is how you implement a Builder Design Pattern -
using System; public class Sandwich { public string Bread { get; set; } public string Jam { get; set; } } public class SandwichBuilder { private Sandwich sandwich = new Sandwich(); public SandwichBuilder AddBread(string bread) { sandwich.Bread = bread; return this; } public SandwichBuilder AddJam(string jam) { sandwich.Jam = jam; return this; } public Sandwich Build() => sandwich; } class Program { static void Main(string[] args) { var sandwich = new SandwichBuilder().AddBread("Whole wheat").AddJam("Strawberry").Build(); Console.WriteLine($"Sandwich: {sandwich.Bread} bread, {sandwich.Jam} jam"); } }
This is how you implement an Adapter Design Pattern -
using System; public class Adaptee { public void SpecificRequest() { Console.WriteLine("Adaptee's specific request"); } } public class Adapter { private readonly Adaptee adaptee; public Adapter(Adaptee adaptee) { this.adaptee = adaptee; } public void Request() { adaptee.SpecificRequest(); } } class Program { static void Main(string[] args) { Adaptee adaptee = new Adaptee(); Adapter adapter = new Adapter(adaptee); adapter.Request(); } }
This is how you implement a Template Design Pattern -
using System; public abstract class AbstractClass { public void TemplateMethod() { Console.WriteLine("Step 1"); Console.WriteLine("Step 2"); Console.WriteLine("Step 3"); } } public class ConcreteClass: AbstractClass {} class Program { static void Main(string[] args) { new ConcreteClass().TemplateMethod(); } }
This is how you implement a Composite Design Pattern -
using System; using System.Collections.Generic; public class Manager { private string name; public Manager(string name) => this.name = name; private List<string> subordinates = new List<string>(); public void AddSubordinate(string employee) => subordinates.Add(employee); public void Display() { Console.WriteLine($"Manager: {name}"); foreach (var subordinate in subordinates) { Console.WriteLine($"- {subordinate}"); } } } class Program { static void Main(string[] args) { Manager ceo = new Manager("John CEO"); Manager cto = new Manager("Bob CTO"); ceo.AddSubordinate("James Developer 1"); ceo.AddSubordinate("Emily Developer 2"); cto.AddSubordinate("Sarah Recruiter 1"); ceo.Display(); cto.Display(); } }
This is how you implement an Iterator Design Pattern -
using System; using System.Collections; public class Iterator { private ArrayList items = new ArrayList(); private int index = 0; public void AddItem(object item) => items.Add(item); public bool HasNext() => index < items.Count; public object Next() => HasNext() ? items[index++] : throw new InvalidOperationException("End of collection reached"); } class Program { static void Main(string[] args) { Iterator iterator = new Iterator(); iterator.AddItem("Item 1"); iterator.AddItem("Item 2"); iterator.AddItem("Item 3"); while (iterator.HasNext()) { Console.WriteLine(iterator.Next()); } } }
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To summarize, Software Design Patterns offer a plethora of benefits to software developers including scalability, reusability, improved code maintainability to mention a few. They offer predefined solutions to commonly occurring problems which promote best practices during development of software. However, it's essential to use patterns judiciously and consider their applicability within the specific context of each project. Blindly applying patterns without understanding their implications can lead to unnecessary complexity and overhead. Developers should always strive for an approach which is balanced, leveraging patterns wherever it is best suited while remaining open to alternative solutions when necessary. Once a developer understands the advantages and limitations of Software Design Patterns, then only they can make informed decisions.
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A Single Pattern ensures that a class has only one instance. A Singleton pattern is used when a class in your application should have only a single instance, for example, a database class. And when you need stricter control over the global variables.
Adapter Pattern bridges the gap between two incompatible interfaces and lets them work together whereas Decorator Pattern dynamically adds new behaviors/responsibilities to an object without altering its structure.
Software Design Patterns are the pre-defined blueprint or universal recipes for solving commonly occurring Design problems. They are not language-specific and can be used in any programming language.
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