What are software engineering design patterns?

Software engineering design patterns offer solutions to software engineers for common problems found within projects. They aren’t pieces of code or templates that can be directly transferred into their work, rather they are blueprints for solutions that can be used to resolve issues.

The design patterns help speed up the software engineering process by helping developers move past common roadblocks. They aren’t quick fixes and they certainly aren’t intended to be an alternative to classic software engineering problem-solving. Instead, they allow developers to tap into the experience that others have had before them and use it to their advantage in projects.

There are mixed opinions about the use of design patterns and so it is interesting to discuss what they are, when they might be of benefit, and what could go against their case.

Let’s discuss.

Types of software engineering design patterns

There are typically thought to be 23 design patterns used in software development and engineering. These can be further split into three categories, which we will explore below. The categories outline the intent of the pattern and all patterns within the category are relevant to the overall intent.

Creational

The first category is creational in intent. Design patterns in this category are used to help software developers create something. They offer pointers to which object should be created in a given scenario. This helps to speed developers along in their creation and initialisation processes.

This category includes the design patterns of Factory Method, Abstract Factory, Builder, Prototype, and Singleton.

Structural

The second category, structural, helps engineers construct larger structures from objects and classes.

The patterns in this subset include Adapter, Bridge, Composite, Decorator, Facade, Flyweight, and Proxy.

Behavioural

Thirdly, the behavioural category focuses on how objects communicate and assign responsibilities.

In this category, we have the Chain of Responsibility, Command, Interpreter, Iterator, Mediator, Memento, Observer, State, Strategy, Visitor, and Template Method.

The benefits

The reasons that many software developers and engineers choose to use design patterns include…

Using tested, trialled, and proven solutions: Software development can involve a lot of trial and error, in which developers test, develop, and redesign consistently throughout a project. Using engineering design patterns helps speed this process along as they are able to use solutions that have already been proven to work.

No need for refactoring: As the design pattern used by the developer has already been optimised for success, there is no need for refactoring the code in question.

Smaller codebases: Design patterns require less code and therefore there can be smaller codebases for projects, increasing efficiency.

Reusable solutions: As there are so many design patterns which have such a range of solutions, there are many times a developer can use one of these solutions in a project. This cuts down on any wasted time and increases the project’s overall productivity.

Design patterns are all about efficiency and not re-discovering the wheel. They allow developers to lean on work that has succeeded in the past and use this success to push current projects on in a timely manner.

Software development and engineering should always prioritise optimisation and efficiency, and that is exactly what software engineering design patterns do too.

The potential drawbacks

However, it is also key to note that design patterns sometimes come under fire, as some people see flaws in their functioning.

Some posit that using design patterns allows developers to choose a lazier option, which can lead to duplicated and defunct code choices. Rather than creating something from scratch that fixes the particular problems related to their project and the current feature they are working on, some say it allows them to pick a more mass-produced solution that may not entirely be the best fit.

Others also challenge the less-than-formal grounds on which design patterns were created, with a lack of theory and proof.

Ultimately, whether software engineering design patterns are used within a project or not will depend on the opinion of the developers and software development companies involved. Some boosts in efficiency can be great but if they are being used as a quick fix rather than being the right solution, some hesitation could be required.

Choices made within software development projects should always prioritise the value of the future end product, the satisfaction of the client, and the integrity of the development company involved. If a design pattern can fit all of those criteria, it can be a beneficial helper to any project.