The Ultimate Guide to Types of Design Patterns [2023]

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Design patterns are repeatable solutions to commonly occurring software design problems. By using design patterns, developers can save time and create more efficient and robust software. In this article, we will dive into the different types of design patterns and how they can be applied to various software design problems.

Introduction to Design Patterns

Before we dive into the types of design patterns, let's first understand what design patterns are. Design patterns are reusable solutions to common software design problems. These solutions have been tried and tested over time to ensure their effectiveness.

What Are the Benefits of Using Design Patterns?

Using design patterns in software design can provide a number of benefits including:

  • Improved readability and maintainability
  • Faster development time
  • Reduced errors and software bugs
  • Increased code quality
  • Reusable design solutions

In the next sections, we will go through the three main types of design patterns: creational, structural, and behavioral.

Creational Design Patterns

Creational design patterns focus on the creation of objects. The goal is to create instances of classes and objects without exposing the underlying implementation details.

Singleton Design Pattern

The Singleton Design Pattern is a creational design pattern that restricts the instantiation of a class to one object. This is useful when only one object should be created to handle all calls to a class.

Pros:

  • Guarantees only one instance of the class will exist
  • Provides access to a single point of control
  • Efficient

Cons:

  • Difficult to test
  • Can introduce Global state

Examples:

  • Logging classes
  • Database handler classes

Factory Method Design Pattern

The Factory Method Design Pattern is a creational design pattern that provides an interface for creating objects, but allows subclasses to determine which class to instantiate. This is useful when there is a need for flexibility in creating objects.

Pros:

  • Encapsulates object creation
  • Improves flexibility
  • Easy to extend and modify object creation

Cons:

  • Requires additional complexity
  • Difficult to test

Examples:

  • Car manufacturer factories
  • Database schema migration

Abstract Factory Design Pattern

The Abstract Factory Design Pattern is a creational design pattern that provides an interface for creating families of related or dependent objects without specifying their concrete classes. This is useful when there are related objects that need to be created, but the specifics of the objects are not known.

Pros:

  • Encapsulates object creation
  • Improves flexibility
  • Easy to extend and modify object creation

Cons:

  • Requires additional complexity
  • Difficult to test

Examples:

  • UI layout factories
  • Web page theme factories

Structural Design Patterns

Structural design patterns focus on the composition of objects to form larger structures. This allows the creation of complex objects and structures using simple objects that can be reused.

Decorator Design Pattern

The Decorator Design Pattern is a structural design pattern that allows objects to be modified without changing the underlying class. This is useful when there is a need to add behavior or features to an object without changing the source code of the object.

Pros:

  • Easy to add functionality to an object
  • Objects can have multiple decorators

Cons:

  • Can lead to a large number of small classes
  • Difficult to remove a decorator once it is added

Examples:

  • CSS stylesheets
  • Logging decorators

Adapter Design Pattern

The Adapter Design Pattern is a structural design pattern that allows objects with incompatible interfaces to work together. This is useful when there is a need to convert one interface to another.

Pros:

  • Can reuse existing code
  • Allows for new classes to be created independently

Cons:

  • Requires additional code
  • Can possibly decrease performance

Examples:

  • Language translation services
  • Payment gateway adapters

Facade Design Pattern

The Facade Design Pattern is a structural design pattern that provides a simplified interface to a complex system. This is useful when a complex system needs to be integrated into a larger system.

Pros:

  • Simplifies the use of complex systems
  • Reduces the complexity of the code

Cons:

  • Can be a performance bottleneck
  • Can lead to unnecessarily complex code

Examples:

  • Database access classes
  • Media player controls

Behavioral Design Patterns

Behavioral design patterns focus on the behavior and communication between objects. This allows objects to communicate more efficiently and effectively.

Command Design Pattern

The Command Design Pattern is a behavioral design pattern that encapsulates a request as an object, thereby allowing requests to be handled in a similar way as objects. This is useful when there is a need to implement a queue of requests.

Pros:

  • Allows for the implementation of undo and redo features
  • Supports queueing of requests

Cons:

  • Can increase complexity
  • Can require additional classes

Examples:

  • Game controls
  • Remote control buttons

Observer Design Pattern

The Observer Design Pattern is a behavioral design pattern that allows objects to be notified of changes in other objects. This is useful when there is a need for two or more objects to communicate with each other.

Pros:

  • Objects can communicate without knowing about each other
  • Enables loose coupling between objects

Cons:

  • Can become complex
  • Can lead to performance issues

Examples:

  • Stock market updates
  • Chat applications

Template Method Design Pattern

The Template Method Design Pattern is a behavioral design pattern that defines the skeleton of an algorithm in a superclass, but allows subclasses to override specific steps of the algorithm without changing the overall structure of the algorithm. This is useful when there is a need for a flexible and customizable algorithm.

Pros:

  • Encourages reuse of code
  • Provides extensibility

Cons:

  • Can be inflexible if not properly implemented
  • Can lead to duplicated code if overused

Examples:

  • Digital signal processing
  • Image processing

FAQ

How many types of design patterns are there?

There are three main types of design patterns: creational, structural, and behavioral, each with a number of specific patterns.

Are there only 23 design patterns?

No, there are more than 23 design patterns. The 23 design patterns mentioned in the book "Design Patterns: Elements of Reusable Object-Oriented Software" by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides are just the most popular and well-known patterns.

What are the main categories of design pattern?

The main categories of design pattern are creational, structural, and behavioral.

Quick Tips and Facts

  • Design patterns are reusable solutions to commonly occurring software design problems.
  • Using design patterns in software design can provide a number of benefits including improved readability and maintainability, faster development time, and increased code quality.
  • The three main types of design patterns are creational, structural, and behavioral, each with a number of specific patterns.
  • There are more than 23 design patterns, despite the book "Design Patterns: Elements of Reusable Object-Oriented Software" only listing 23.
  • Using design patterns can make a software application more efficient, scalable, and easier to maintain over time.

Conclusion

Design patterns provide software developers with repeatable solutions and approaches to common software design problems. By using these patterns, developers can create more efficient and maintainable code. Remember, different design patterns can be combined to create even more powerful solutions to software design problems.

When choosing which design pattern to use, consider the specific problem that needs to be solved, and how the pattern can be applied to that problem. By using design patterns, you can increase code quality and make your application more efficient, scalable, and easier to maintain over time.

We hope this article has provided valuable insights into the different types of design patterns and their applications. Happy programming!

References

  • Design Patterns: Elements of Reusable Object-Oriented Software by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides
  • Head First Design Patterns: A Brain-Friendly Guide by Eric Freeman and Elisabeth Robson
  • Refactoring: Improving the Design of Existing Code by Martin Fowler.
Jacob
Jacob

Jacob is a software engineer with over 2 decades of experience in the field. His experience ranges from working in fortune 500 retailers, to software startups as diverse as the the medical or gaming industries. He has full stack experience and has even developed a number of successful mobile apps and games.

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