What are Design Patterns?

What Are Design Patterns?

While developing a software solution, various discussions take place to plan and determine the best possible procedure for the product development process. In this process, the group of developers may be unable to come up with a commonly accepted approach to solve a specified real-world problem. Due to differences in their problem-solving approach, software developers provide various unique ways of building object-oriented software applications that solve a particular problem.

This uniqueness can lead to developer-favored variations in source code that can make the software difficult to distribute, extend, reuse, and manage by fellow developers. Hence, there is a need for standardization in the case of object-oriented software.

This problem of standardization was solved with the introduction of Design Patterns in 1995 in the Design Patterns: Elements of Reusable Object-Oriented Software book (also called the Gang of Four) which was written by Erich Gamma, John Vlissides, Ralph Johnson, and Richard Helm.

The Gang of Four authors observed some commonly occurring problems in object-oriented software design and came up with some descriptive solutions to those recurring problems. These solutions to repeating problems in software design are known as Design Patterns. Each design pattern is a template or a description that provides a way to structure the classes and objects in object-oriented software.

These design patterns were a result of well-tested and proven object-oriented design techniques that can be used to solve a particular design problem. As a result, the design patterns are considered a standard in object-oriented software design i.e., if you want to build an object-oriented software using best practices, then you should follow the Software Design Patterns.

A Design Pattern is identified by how it solves an object-oriented problem or issue. For example, the Bridge Pattern eradicates the dependency between the Abstraction and its Implementation by creating an object-composition link (bridge) between them.

A Brief History Of Design Patterns And The Gang Of Four

A pattern is a repetitive design that can only be discovered and observed. Similarly, the Software Design Patterns were first discovered and described formally in 1995 by the so-called Gang of Four book authors Erich Gamma, John Vlissides, Ralph Johnson, and Richard Helm.

They took inspiration from the work of Christopher Alexander and his colleagues on architectural patterns (published in 1977) and observed the similarities between software design and architectural patterns. They applied the concept of patterns to object-oriented software design and formulated 23 design patterns, each of which solved a particular object-oriented design problem or issue.

These 23 design patterns were categorized into three different groups based on the pattern's intent and purpose. These groups are :

• Creational Patterns :- The traditional method of object creation can lead to the instantiation of objects in an uncontrolled fashion. It can scatter objects all over the application which can increase the overall application design complexity. This can make an object-oriented application unstable and can lead to design problems. Creational Design Patterns reduce this design instability and complexity by providing different ways to implement controlled object creation in an object-oriented application. There are 5 different creational design patterns, namely :
  • Singleton pattern
  • Factory pattern
  • Abstract Factory pattern
  • Builder pattern
  • Prototype pattern
• Structural Patterns :- Structural Design Patterns provide different ways to organize the classes and objects in an object-oriented application such that it leads to simplification of the design of large and complex structures. It describes the process using which we can combine classes and objects to form an organized, flexible, and connected structure. There are 7 different types of structural design patterns. These include :
  • Adapter pattern
  • Composite pattern
  • Proxy pattern
  • Fly Weight pattern
  • Facade pattern
  • Bridge pattern
  • Decorator pattern
• Behavioral Patterns :- Behavioral design patterns deal with the interaction of objects with each other. These patterns follow the fact that the objects in an object-oriented application should be interconnected in such a way that hard coding can be avoided and the user input can be well handled. These design patterns make use of loose coupling techniques to ensure a flexible and effective flow of information. Behavioral design patterns include 12 different patterns namely :
  • Chain of Responsibility Pattern
  • Command Pattern
  • Interpreter Pattern
  • Iterator Pattern
  • Mediator Pattern
  • Memento Pattern
  • Observer Pattern
  • State Pattern
  • Strategy Pattern
  • Template Pattern
  • Visitor Pattern
  • Null Object Pattern

Why Should You Learn Design Patterns?

Design patterns are a toolkit of tried and well-tested solutions to common software design problems created by experienced object-oriented practitioners. Every software developer should have the knowledge of design patterns as :

• Design patterns make our life easier by providing ready-made design templates that make object-oriented systems more flexible, more resilient to change, and easier to maintain.
• We can improve our object-oriented programming skills just by learning about the design patterns as design patterns provide guidelines that teach us to solve all sorts of common object-oriented design problems.
• Design Patterns define a common language that a software developer can use to communicate and collaborate with other developers. Developers can use the name of the design pattern to perfectly explain the ideology behind the application design.

How To Study And Use Design Patterns?

After learning the basics of object-oriented programming, one should follow the three-step learning process given below :

• Acceptance: First, try to accept the fact that design patterns solve commonly occurring problems in object-oriented software design. Hence, when we are developing any object-oriented software we should not complicate the process by reinventing the wheel.

• Recognition: Recognize the importance of following the best practices while developing object-oriented software applications. Read about the problems that are solved using design patterns and identify similar problems in your own development work. In this way, we may find a way to use these design patterns efficiently.

• Internalization: Once a suitable design pattern is identified for our software application, we can try to implement it and add it internally to our application in such a way that it provides reusability, manageability, and extensibility.

Benefits Of Design Patterns

The benefits of using Design Patterns in object-oriented software development are :

• Since Design Patterns are considered best practices for object-oriented software design, they can speed up the software development process by providing efficient paradigms.
• Design Patterns help a developer to communicate and collaborate with other developers at an abstract level as they are considered industry-standard in object-oriented software design and are well known among the developer community. Instead of describing the whole structure of the application, we can directly use the name of the design pattern to explain the software design ideology and implementation to fellow developers.
• Design patterns are reusable in multiple projects and they may prevent subtle issues that can cause havoc later. This is because design patterns provide the logical and efficient solution to a particular and commonly-occurring software design problem without considering the actual implementation.
• Using design patterns provides transparency to the design of application architecture and increases the understanding and readability of the source code. The whole architecture of an object-oriented software application can be logically described by the name of the design pattern used in that application. This provides the transparency that allows developers to collaborate and understand the software design and implementation of an object-oriented application.