A Step-by-Step Guide to Refactoring with Design Patterns

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Software engineering is a broad area in the field of information technology. It involves software developers designing and developing applications according to client requirements and specifications. The process of software development flows along the software development lifecycle and one of the major phases of the cycle is design. 

Design is defined as the virtual process of architecture, components,  and interfaces. Software design is often seen as a form of solving problems and the main expectation is to produce a high-quality system. At present, the object-oriented approach of software designing is used to manage the complexity of real-world problems. This approach includes different elements including the object, class, inheritance, polymorphism, encapsulation, and aggregation.

Nevertheless, The solid foundation of the design phase is the software refactoring with design patterns that are introduced.

A Push through Design Patterns in Software Development

Design patterns are defined as reusable solutions to generally occurring specific problems. The concept of design patterns came to light by the publication of ‘Elements of Reusable Object-Oriented Software’. Therefore the pioneers of design patterns are considered to be the Gang of Four.

Refactoring with design patterns

A design pattern produces a solution to the problem in terms of organization, class, and objects that is generally used in problem-solving. The design patterns can be used in various situations with minor modifications to suit the problem. Design patterns provide pathways to refine the components of the software system and aid in describing the recurring structures of the components involved with the design problem. 

A design pattern includes a pattern name, problem description, solution, and, consequence sentient, all of which attributes to the functioning of the design patterns. Furthermore, design patterns can be categorized into four major classes as follows

  • Creational Design Pattern
  • Structural Design Pattern
  • Behavioral Design Pattern
  • JEE Design Pattern

Different subclasses of design patterns are distributed among the above 4 classes according to its functionality. Thereby, the refactoring design pattern examples also fall under the same categories.

Designing is majorly focused on maintaining the quality and efficiency of the system it develops. Quality is a fundamental property of software systems and high quality shows that it has the required characteristics, tools, and techniques. Quality focuses on functionality, reliability, usability, efficiency, maintainability, and portability. System and software quality is majorly improved and protected with the process known as refactoring. Thereby, this review will focus on everything that you need to know about refactoring with design patterns and the process of applying design patterns during refactoring.

What is Refactoring?

In context with software development, refactoring is simply a reengineering technique that was initially introduced by Opdyke. With the use of refactoring the quality of a program could be enhanced without doing any changes to the external behavior. Refactoring improves the quality of the system without altering the primary functionality of the system.

Following a failed design, the code could be modified with the use of the process of refactoring. Thus, changing the design to a complete success.

Refactoring could be used for several purposes such as improving the design quality, easier addition of codes, helping in finding bugs, and aiding in making a program faster.

Refactoring has its own techniques and it could not be used at every point. This process has to be used cautiously on the proper points of the designs. Nonetheless, Refactoring common design patterns is highly used in the field today.

Design Smell and Code Smell

Design Smell

Design smell and code smells are generally introduced as the structures that are used to identify when to apply the refactoring. Design smells are certain structures in a design that points out violations in the fundamental design patterns which would cause a reduction of system quality. Simply, design smells show a problem in the design architecture. 

Design smells choose a design to be bad due to various reasons such as

  • Violation of the principle of designing
  • Inappropriate use of design patterns
  • Limitations of programming languages
  • No adhering to the best practices of design architecture.

Furthermore, design smells are classified into 4 groups according to the violations and mistakes it identifies and the groups include

  • Hierarchy
  • Modularity
  • Encapsulation
  • Abstraction

Code Smell

Duplication of codes and unclear or complicated codes are some of the most common design problems resulting. These design problems could be identified by code smells which were initially introduced by Martin Fowler and Kent Beck. These code smells are well-defined and target problems in methods, classes, hierarchies, and even entire systems.

For different code smells identified an appropriate refactoring method is used. Shown below are some of the code smells and the refactoring methods in action

  • For Duplicated method – Form Template Refactoring Method, Chain Constructors
  • For Long method – Compose Refactoring Method
  • For Conditional complexity – Replace Conditional Logic with Strategy

Process to Refactoring with design patterns

design patterns

The process of refactoring is systematic and is performed in an ad-hoc fashion. Refactoring legacy code with design patterns uses a systematic process called IMPACT is utilized in refactoring that is comprised of four fundamental steps as mentioned below

  • Identifying refactoring candidates

In this step, the analysis of the codes takes place to identify any codes violating the design patterns. Here code and ensign smells are used for the process. 

  • Planning refactoring activities

After identification of the codes, they have to be prioritized according to the depth of violation and then an execution plan for refactoring should be assessed. The depth of violation is based on the severity, scope, and interdependence. According to the prioritized code smells the selection of appropriate design patterns could be done based on the smell.

  • Acting on the planned refactoring tasks

The refactoring tasks could be divided among team members and the tasks could be carried out

  • Testing to ensure behavior preservation

Following the refactoring actions, automated regression tests will be performed to test the behavior of the system and to make sure that the environment has remained unchanged. This step is the most important step in refactoring.

The performance is measured by different aspects of measurements as depicted below

  • Measuring the complexity of the refactored application

Using this application,  a summarized detailed list of the refactored designs will be produced with the number of classes, packages, methods, and total lines of codes.

  • Dynamic Performance Efficiency Measuring

This activity measures the performance through core performance testing. The criteria included identifying the test environment, identifying performer acceptance criteria, planning and designing tests, configuring the test environment, Implementing test design, executing tests, and Analyzing reports and Retest.

Benefits of Refactoring for Design Patterns

The benefits of using design patterns for refactoring are high. It makes the codes easier to read and therefore debugging will not take a lot of time and more time could be utilized for other tasks. Furthermore,it makes it easier to onboard new developers since code refactoring allows to have a styled guide. As mentioned, the performance could be greatly increased and will allow fast-running applications. Lastly, the applications could be moved to the modern cloud as the code refactoring leads to efficient performance, and thus, new features could be added easily.

Drawbacks of Refactoring for Design Patterns

The entire refactoring process is time-consuming and mostly it is quite costly as well.

In Conclusion

Code Refactoring is an important aspect of Software development. It aids in the process of producing error-free design architectures. Thereby, it enhances the quality and efficiency of software by using various refactoring implementations once violations are found. Although advantageous, refactoring has its own drawbacks too. The best practices for refactoring with design patterns are massive. Nonetheless, refactoring codes for design patterns are indeed a software developer’s best friend!

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