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Software Design Patterns

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Introduction

Software design patterns are the proven practices/paradigms experienced software developers use worldwide to produce good quality software. It ensures that the final product is reusable and maintainable.

Software Design Patterns

This article will discuss the benefits and classification of software design patterns.

What are Software Design Patterns?

Software Design patterns are well-tested and solutions to the recurring problems in software development. They are used in object-oriented programming to make the software reusable, understandable, maintainable, and flexible. These are not mandatory practices to be followed to produce good software but using software design patterns helps make it easier and faster for the developers. 

Software design patterns

Software design patterns are the abstract ideas for developing well-tested software and not the actual implementation; hence it is free of the programming language. It is important to understand software design patterns as, unlike the implementation, it cannot be copied from any platform. 

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How are Patterns Described?

Software design patterns are typically described using a consistent format that includes the following elements:

  • Pattern Name: Clearly identifies the pattern with a descriptive name.
     
  • Intent: Defines the problem that the pattern aims to solve. It articulates the goal and purpose of applying the pattern.
     
  • Motivation: Explains the scenario or context in which the pattern is beneficial, providing real-world examples or use cases to illustrate its relevance.
     
  • Applicability: Specifies the conditions under which the pattern is applicable, helping developers understand when and where to apply the pattern.
     
  • Structure: Illustrates the components of the pattern and their relationships. It often includes diagrams or diagrams to visually represent the pattern's structure.
     
  • Participants (Classes/Objects): Lists the classes or objects involved in the pattern, along with their responsibilities and collaborations.
     
  • Collaborations: Describes how the participants collaborate to fulfill the pattern's intent, detailing the communication and interactions between components.
     
  • Consequences: Outlines the trade-offs and implications of applying the pattern. This includes the benefits and drawbacks developers should consider.
     
  • Implementation: Provides guidance on how to implement the pattern in code, including example code snippets and considerations for different programming languages.
     
  • Known Uses: Highlights examples of real-world systems or projects that have successfully applied the pattern.
     
  • Related Patterns: Identifies other design patterns that are related to or can complement the discussed pattern. It helps developers explore additional solutions.
     
  • References: Cites sources, articles, or books where readers can find more in-depth information about the pattern.

Why use Software Design Patterns

Following are the benefits of using software design patterns:

  • It speeds up the process of software development by providing previously used and well-tested solutions to recurring problems.
     
  • It makes the code understandable and readable for coders familiar with the pattern.
     
  • As the solution is previously used and tested, the chances of failures/errors are more petite.
     
  • Common software design patterns can be improved over time by considering more variables to develop more robust solutions.
     
  • Provides faster and easier practices for problem-solving. 
     
  • It makes communications among coders and developers easier by using standard techniques and names for solutions. 
     
  • It ensures that the final product is reusable and maintainable.

Classification of Software Design Patterns 

Based on purpose and intent, software design patterns are classified into three main categories. 

They are:

  • Creational
  • Structural
  • Behavioral

Classification of software design patterns

All the software design patterns can be kept under one of the above three categories. There are around 26 software design patterns. 

Now we will discuss each of the categories in detail.

Creational Software Design Patterns

These software design patterns are used for object creation, initialization, and class instantiation. What type of object should be initiated, what class object is to be instanced are the few problems solved by creational software design patterns. These can be further classified into class creational and object creational software patterns. These are used to improve the code reusability and flexibility.

Example

Suppose we are building a game where new players are joining continuously with new names as a guest. In such a case many instances of players will be created to work as a guest, but as soon as the person closes the game the guest player instance is of no use anymore. Such instances can be stored in an object pool and can be used when a request to create a new guest player is made. 

Following are the Creational Software Design Patterns:

Creational software design patterns

  • Singleton: It ensures that only one object can be created for a class. A global access point is provided to this instance. You can also check about Singleton Design Pattern C#.
     
  • Prototype: Creating copies/clones of an already existing object without using inheritance. Here the copy does not depend upon the class of the object it is cloned from.
     
  • Abstract Factory: It creates families of related objects without involving the classes. This helps us create new object variants without manipulating the existing client code. 
     
  • Factory Method: Create an interface with several classes to instantiate an object. The subclasses define the type of object. It can be used when we want to do the same thing, but the method differs on different platforms. Using this, you can gather the code for object creation in one place, making it easier to understand. A new variant can also be created without altering the existing classes.
     
  • Builder: It breaks the process of complex object creation into steps so that it becomes easier to keep track of the functionalities of the object. This can be used to create objects of the same class with slight differences. 
     
  • Object Pool: The object Pool is also known as a resource pool, containing the objects that are instantiated and not in use. It is helpful in classes where object instantiation is costly and time-consuming. We use an object from the object pool instead of instantiating a new object each time. 

Structural Software Design Patterns

Structural Software Design Patterns are the practices that are used for developing different compositions of classes and objects. Here, you can create new objects with new functionalities that may be a composition of two or more existing classes. They make the software more efficient and flexible. 

Example

Suppose you are building an application where you get the input in XML format, now if you want to add a new feature to the existing application and that feature needs the data in JSON format. In such situation you can use the Adapter structural design pattern. Adapter allows the objects in an application to adapt to incompatible interfaces/formats and work together.

Following are the Structural Software Design Patterns:

Structural software design patterns

  • Adapter: It allows the objects to adapt to incompatible interfaces and work together. 
     
  • Bridge: It is used to split the larger or loosely related classes into abstraction and implementation. It is used to create platform-independent software. It reduces the program's complexity by dividing the errors to be dealt with separately with the higher-level abstraction part and the core implementation.
     
  • Facade: Provides a streamlined interface to a library, framework, or any other complex collection of classes. It is like a simplified API that abstracts the low-level implementational details. It makes our code more readable and understandable by isolating the complex helper code from the high-level application code.
     
  • Proxy: Proxy means to substitute an object with another object. It is used mainly when the object is complex and difficult to duplicate in memory.
     
  • Composite: It is used where you can represent an object as a tree. You can use a tree structure to compose an object and let the clients work with these objects as if it is an individual objects.
     
  • Decorator: Dynamically attach new functionalities to objects by wrapping the object inside a special wrapper containing those new functions. It allows us to add or remove responsibilities or functionalities at run time.
     
  • Flyweight: It helps in memory management. Multiple objects share the common space for storing the exact details rather than consuming separate memory.
     
  • Private class data: Defining data attributes as private will restrict the undesired manipulations. It ensures that no unwanted manipulations are made on data attributes by controlling the write access. 

Behavioral Software Design Pattern

Behavioral software design patterns are the patterns associated with the communication between objects. These are the patterns that are concerned with the responsibility assigned to objects. By using these patterns, you can get flexibility in communication. 

Example

Suppose we are building an application where we have a lot of components and there are components inside other components. In such applications when we want to access an information then we can use a chain of responsibility that reachs the outermost component first and then moves inner and inner until it reaches the desired component. 

Following are the Behavioral Software Design Patterns:

Behavioral Software Design Patterns

  • Chain of responsibility: This pattern creates a chain of handlers responsible for passing the information/request to the desired handler. A handler can either process the request or pass on the request to the next handler. 
     
  • Command: This converts any request into an object. This object contains all the information regarding the request. This allows us to pass the request like an object to functions, delays, or queues. 
     
  • Interpreter: This pattern allows to include of language in the program. 
     
  • Iterator: It is used to traverse the elements in a sequential order without understanding the unlying data structure used. 
     
  • Mediator: This allows the objects to communicate without establishing direct communication. You can introduce new mediators anytime without changing the basic components. 
     
  • Memento: It is used to save and restore the internal state of an object without revealing the inner implementational details. It is like taking a snapshot of an object's state without violating its encapsulation.
     
  • Null Object: It is mainly used as a default value to deal with missing values or at the initialization time. 
     
  • Observer: Observers are like reporters for objects that notify multiple other objects about the events associated with the objects they are observing. 
     
  • State: This pattern lets objects know what to do or alter when they change their internal state. 
     
  • Strategy: It lets you define multiple algorithms separated into different classes and make their objects interchangeable.
     
  • Template Method: It defines the blueprint of an algorithm in the superclass that can be modified in the subclasses without changing its structure. It ensures code reusability.
     
  • Visitor: It allows you to define new operations on the objects of different classes without redefining or changing the classes. 
     

Usage of Design Patterns in Software Engineering

The usage of design patterns in software engineering are:

  • Design patterns provide abstract solutions to recurring design problems. They promote code reusability, allowing developers to apply proven solutions to common challenges.
     
  • Patterns facilitate scalable software architecture by offering modular and maintainable design approaches. This scalability is crucial for handling growth and evolving requirements.
     
  • Design patterns serve as a common language for developers. They enable effective communication and understanding among team members, fostering collaboration and consistency in software design.
     
  • Patterns encapsulate best practices in software engineering. Following established patterns helps ensure that solutions are well-tested, understood, and have a track record of success.
     
  • Patterns guide developers in solving specific design problems. They provide a roadmap for addressing challenges and offer insights into structuring code for optimal performance and maintainability.
     
  • By promoting clean, modular designs, patterns enhance code maintainability. This is crucial for reducing technical debt and ensuring that software remains adaptable to future changes.

Patterns vs Algorithms

There are various differences between patterns and algorithms:

  • Scope: Design patterns focus on higher-level, architectural solutions to recurring design problems. They address the organization and structure of software components. Algorithms, on the other hand, are step-by-step procedures for solving specific problems or performing computations. They are more granular and task-oriented.
     
  • Level of Abstraction: Patterns abstract over design issues and provide generalized solutions applicable to a range of problems. While algorithms deal with specific sequences of steps for solving a particular problem, often at a lower level of abstraction.
     
  • Purpose: Patterns emphasize design and architecture, providing guidelines for creating scalable, maintainable, and modular software. On the other hand, algorithms focus on the efficiency and correctness of a specific computation or task.
     
  • Applicability: Design patterns are reusable across various contexts and scenarios, providing solutions to common design challenges. While, algorithms are task-specific and may not be as easily reusable for different problems.
     

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Frequently Asked Questions

What are Software Design patterns?

Software design patterns are the proven practices/paradigms experienced software developers use worldwide to produce good quality software. It ensures that the final product is reusable and maintainable.

What is coding design pattern?

A coding design pattern is a reusable solution to a common programming problem. It provides a template for structuring code to enhance clarity, maintainability, and efficiency.

How many patterns are there in software engineering?

There isn't a fixed number, but there are numerous design patterns. Common ones include creational, structural, and behavioral patterns, each addressing specific aspects of software design.

What is the purpose of a design pattern?

The purpose of a design pattern is to provide a proven and reusable solution to common software design problems. It promotes best practices, modularity, and maintainability in code.

Conclusion

This article discussed software design patterns. Design patterns stand as the architectural blueprints that elevate software engineering to new heights. From fostering code reusability to enhancing maintainability and scalability, these patterns serve as beacons of best practices. As we navigate the complex landscape of software development, embracing these proven solutions becomes paramount.

Recommended Readings:

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Topics covered
1.
Introduction
2.
What are Software Design Patterns?
3.
How are Patterns Described?
4.
Why use Software Design Patterns
5.
Classification of Software Design Patterns 
5.1.
Creational Software Design Patterns
5.2.
Structural Software Design Patterns
5.3.
Behavioral Software Design Pattern
6.
Usage of Design Patterns in Software Engineering
7.
Patterns vs Algorithms
8.
Frequently Asked Questions
8.1.
What are Software Design patterns?
8.2.
What is coding design pattern?
8.3.
How many patterns are there in software engineering?
8.4.
What is the purpose of a design pattern?
9.
Conclusion