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10 Best Software Design Patterns in 2024 [Types & Benefits]

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25th Apr, 2024
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    10 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.

    What is a Software Design Pattern?

    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.

    Why Do We Need Software Design Patterns?

    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?

    • Software Design patterns are very well tried and tested solutions to commonly occurring problems in Software Design.
    • They save a lot of time; developers can quickly use Software Design Patterns instead of reinventing the wheel.
    • They make it easier to change the software because the code has been designed using the best coding practices.
    • Most of the patterns make the software efficient and increase the performance by decreasing the response time.

    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.

    Types of Software Design Patterns?

    Software Design Patterns are categorized into three types namely -

    • Creational Patterns
    • Structural Patterns
    • Behavioral Patterns

    Types of Software Design Patterns
    gustavopeiretti

    1. Creational Patterns

    Below are the Creational patterns in Design Patterns -

    • Singleton: This pattern ensures that a class has one and only one instance and provides a global point of access to it.
    • Factory Method: This pattern defines an interface for creating objects but allows subclasses to alter the type of objects that will be created.
    • Abstract Factory: This pattern provides an interface for creating families of related or dependent objects without specifying their concrete classes.
    • Builder: This pattern separates the construction of a complex object from its representation.
    • Prototype: This pattern creates new objects by copying an existing object.

    2. Structural Patterns

    Below are the Structural patterns in Design Patterns -

    • Adapter: This pattern allows incompatible interfaces to work together by providing a bridge between them.
    • Bridge: This pattern decouples the abstraction from its implementation.
    • Composite: This pattern creates tree structures out of objects by composing them to represent part-whole hierarchies.
    • Decorator: This pattern dynamically adds or overrides functionality.
    • Facade: This pattern simplifies the usage by providing a unified interface to a set of interfaces in a subsystem.
    • Flyweight: This pattern shares common parts of objects to reduce memory usage and improve performance.
    • Proxy: This pattern controls access by providing a placeholder for another object.

    3. Behavioral Patterns

    Below are the Behavioral patterns in Design Patterns -

    • Command: This pattern encapsulates a request as an object, allowing for parameterization of clients with queues, requests, and operations.
    • Interpreter: This pattern defines grammar for a language and provides an interpreter to interpret sentences in that language.
    • Iterator: This pattern provides a way to access elements of an aggregate object sequentially without exposing its underlying representation.
    • Mediator: This pattern defines an object that encapsulates how a set of objects interact, promoting loose coupling between them.
    • Memento: This pattern saves an object's internal state to restore its state later.
    • Observer: In this pattern when one object changes its state, all the other objects which are the dependents are automatically notified.
    • State: This pattern allows an object to change its behavior when there is a change in the internal state.
    • Strategy: This pattern defines a family of algorithms, each one is encapsulated and made interchangeable.
    • Template Method: This pattern defines the skeleton of an algorithm in a superclass but let's subclasses override specific steps of the algorithm without changing its structure.
    • Visitor: This pattern represents an operation to be performed on elements of an object structure, allowing new operations to be defined without changing the classes of the elements.

    23 GoF Sofware Design Patterns
    Paulsblog

    10 Best Software Design Patterns

    The most popular Software Design Patterns are as follows -

    1. Singleton Design Pattern

    This is how you implement a Singleton Design Pattern -

    • Make the Singleton class sealed to prevent inheritance.
    • Make the constructor private to prevent instantiating the object directly.
    • Provide a static method GetInstance() which checks if the instance is already present or not and creates it by invoking the constructor if not present else returns the existing instance.
    • Provide a Main() method where you invoke the GetInstance() method twice.
    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));
}
}

    Singleton Design Pattern
    netsolutions

    2. Prototype Design Pattern

    This is how you implement a Prototype Design Pattern -

    • Declare an Interface ICloneableShape with a Clone() method which clones the shape.
    • Provide a class Circle which implements ICloneableShape and provides its own implementation of Clone() method.
    • In the Main() method, create a circlePrototype object and invoke the Clone() method on it to create clonedCircle object which clones circlePrototype object.
    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();
}
}

    Prototype Design Pattern
    Refactoring Guru

    3. Facade Design Pattern

    This is how you implement a Facade Design Pattern -

    • Create two classes SubsystemA and SubsystemB with methods OperationA() and OperationB() respectively.
    • Create a Facade class which provides a PerformOperation() method that encapsulates the complexity of SubsystemA and SubsystemB by providing a simplified interface.
    • Create a Main() method and initialize the facade object which performs the complex operation using PerformOperation().
    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();
}
}

    Facade Design Pattern
    netsolutions

    4. Strategy Design Pattern

    This is how you implement a Strategy Design Pattern -

    • Define classes ConcreteStrategyA and ConcreteStrategyB with their respective Execute() methods.
    • Create a Context class with method SetStrategy() that changes the strategy at runtime and ExecuteStrategy() that executes the dynamic strategy.
    • In Main() method, create the context object and set the strategy to ConcreteStrategyA by using SetStrategy() method. Execute it by invoking ExecuteStrategy() method.
    • Repeat the above step for ConcreteStrategyB.
    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();
}
}

    Strategy Design Pattern
    netsolutions

    5. Observer Design Pattern

    This is how you implement an Observer Design Pattern - 

    • Create a class ConcreteSubject which has RegisterObserver() and NotifyObservers() methods to register and notify the observers respectively.
    • Create a class ConcreteObserver that defines Update() method to receive notification from the ConcreteSubject.
    • In the Main() method, create a subject, register Observer1 and Observer2 and notify them.
    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!");
}
}

    Observer Design Pattern
    netsolutions

    6. Builder Design Pattern

    This is how you implement a Builder Design Pattern -

    • Create Sandwich class with attributes Bread and Jam.
    • Create a SandwichBuilder class that adds bread and jam to the Sandwich step by step by using AddBread() and AddJam() methods respectively.
    • Define a Main() method which builds a sandwich using SandwichBuilder by chaining methods AddBread() and AddJam() thereby returning the sandwich by using Build() method.
    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");
}
}

    Builder Design Pattern
    netsolutions

    7. Adapter Design Pattern

    This is how you implement an Adapter Design Pattern - 

    • Create an Adaptee class with method SpecificRequest().
    • Create an Adapter class that wraps the Adaptee object and provides a method Request() to map to the Adaptee’s SpecificRequest() method.
    • Define a Main() method, create adaptee object and wrap that object within the adapter object by invoking Adapter’s constructor.
    • Call the Adapter’s Request() method which internally invokes the Adaptee’s SpecificRequest() method.
    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();
}
}

    Adapter Design Pattern
    Refactoring Guru 

    8. Template Design Pattern

    This is how you implement a Template Design Pattern -

    • Create an abstract class AbstractClass with a template method TemplateMethod() which defines a fixed sequence of steps.
    • Create ConcreteClass class which extends AbstractClass and inherits TemplateMethod().
    • Define a Main() method which invokes the TemplateMethod() for the instance of ConcreteClass.
    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();
}
}

    Template Design Pattern
    Refactoring Guru

    9. Composite Design Pattern

    This is how you implement a Composite Design Pattern -

    • Create a Manager class and methods AddSubordinate() and Display() to add subordinates under him and display all of them respectively.
    • Define Main() method and create instances of Mananger, ceo and cto.
    • Add two subordinates under ceo and one under cto using AddSubordinate() method and display them using Display() method.
    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();
}
}

    Composite Design Pattern
    Refactoring Guru

    10. Iterator Design Pattern

    This is how you implement an Iterator Design Pattern -

    • Create an Iterator class and add items to the ArrayList by defining method AddItem(), check if the list has next item by defining method HasNext() and get the next element by defining method Next().
    • Define a Main() method and create iterator object.
    • Add 3 items to the iterator using AddItem() method and print them using Next() method by iterating over them using HasNext() method.
    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());
}
}
}

    Composite Design Pattern
    Refactoring Guru

    After having a good exposure on 10 most common Software Design Patterns, are you ready to take your coding skills to the next level? Explore the world of Web Development by enrolling for our Web Development course.

    Benefits of Design Patterns in Software Engineering

    • Reusability: Patterns offer reusable solutions to common problems.
    • Abstraction: They abstract complex implementations into manageable components.
    • Scalability: Enable flexible and extensible architectures.
    • Code Understandability: Promote standardized and easier-to-understand code.
    • Maintainability and Testability: Facilitate easier maintenance and testing of software.
    • Best Practices: Encapsulate best practices and principles of software engineering.
    • Cross-Platform Compatibility: Offer platform-independent solutions.

    Criticism of Software Design Patterns

    • Overhead: Patterns can introduce unnecessary complexity and overhead, especially in simpler applications.
    • Inflexibility: Blindly applying patterns without considering the context can lead to inflexible and over-engineered solutions.
    • Misapplication: Misusing or overusing patterns can result in code that is harder to understand and maintain.
    • Learning Curve: Learning and understanding patterns requires time and effort, which may not always be feasible for developers.
    • One-Size-Fits-All: Not all problems can be effectively solved using patterns and forcing a pattern onto a problem can lead to suboptimal results.
    • Complexity: Patterns can sometimes add unnecessary layers of abstraction, making the codebase harder to understand for newcomers.

    Conclusion

    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. 

    You can take your development skills to the next level by enrolling for KnowledgeHut's Software Engineering online certificate programs.

    Frequently Asked Questions

    1. What is the Singleton pattern, and when is it used?

    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.

    2. What is the difference between the Adapter and the Decorator patterns?

    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.

    3. Are design patterns language-specific?

    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.

    Profile

    Naman Sinha

    Blog Author

    An eminent speaker and author, Naman Sinha's interest lies in empowering people by mentoring them in the IT industry through articles, talks, training and much more. He is an expert passionate about Microsoft technologies.

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