Software Design Patterns 101: What Is It and Why Must You Learn Them?
If you run into a problem during coding or don't know how to code in a more efficient manner, there is a good chance that the solution already exists in the form of a design pattern. Knowledge of how and when to use software design patterns correctly can significantly help developers reduce code complexity and design burden. So, this article is just for you if software design patterns are still not part of your arsenal of development tools or you simply want to refresh your design pattern knowledge.
Software design patterns: the definition and composition
A design pattern describes a reusable solution to a frequently encountered coding problem in a particular context. Note that you can’t just find a suitable design pattern and copypaste it into your code, as you’d do with off-the-shelf functions or libraries. Instead, you need to follow the details of a pattern, understand the way it works, and, based on that pattern, come up with a solution. In other words, you need to figure out how and where to properly apply this approach.
The book “Design Patterns”, written by the “Gang of Four” (Erich Gamma, Richard Helm, Ralph Johnson, and Jonah Vlissides), describes patterns as "problem-solving in context." Three components - the problem, the solution, and the context - are the essence of the pattern. Various authors of patterns have used many different formats to document them, and all of these formats differ in the level of detail and pattern analysis. However, there are several main sections that are usually included in a pattern description:
- Pattern name and classification: a descriptive and unique name that helps identify and reference the pattern;
- Intent: briefly describes the problem and solution that the pattern offers;
- Motivation: a scenario illustrating the problem;
- Structure: a diagram using an object modeling technique (OMT);
- Implementation: implementation details to consider, language-specific issues;
- Example code: executed in one of the popular programming languages, code example makes it easy to understand the idea behind the pattern.
Due to the fact that patterns describe frequently encountered issues they can sometimes be confused with algorithms. The difference between the two is that an algorithm is a clear set of actions to solve a specific problem that is broken down into steps. Whereas software design patterns are more of “blueprints” of solutions to common problems that arise when creating a software solution.
Software design patterns are how you structure algorithms, that is, which algorithms exist in which class. Let's take an analogy with building construction. Algorithms are how the steel frames are welded together and what materials are used, and software design patterns are the architects' plans for how the structure as a whole will function.
Classification of patterns
There are 23 basic software design patterns that have become the point of departure for many object-oriented design problems. All of them vary in complexity, level of detail, and scope of applicability to the entire system. The different types of patterns are divided into three main categories, according to their purpose and goal.
Structural patterns describe how to collect objects and classes into structures while retaining the flexibility and efficiency of those structures. Structural patterns allow you to define relationships between application components and are especially useful in large development systems. Common structural patterns include Adapter, Proxy, Decorator, and Facade.
Creational patterns describe different methods of creating objects that are appropriate for a particular situation. These patterns help reduce the complexity and instability of code while providing increased flexibility and reusability. There are four types of creative design patterns: Singleton, Factory Method, Prototype, and Builder.
Behavioral patterns define how objects should communicate and interact with each other. They help make complex behavior more manageable by defining the responsibilities of objects and ways of their interaction. Key examples of behavioral patterns are Chain of Responsibility, Iterator, Mediator, Observer, and Strategy.
Should you use software design patterns or not really?
Software design patterns are a double-edged sword: if they are used by developers in the right context, they become indispensable and effective solutions to many coding issues. However, the improper use of software design patterns can only make things worse and make your code more cumbersome.
More often than not, developers use patterns when a particular part of the system needs something that matches the design pattern available. It is not obligatory to try to fit a system to a design pattern - it is better to fit software design patterns to your system (where they are needed). In addition, it is useful to occasionally revisit the decisions previously made about software design patterns, because of deficiencies in the software, or as new experiences are gained. For a complete picture of understanding patterns, let's look at them from different angles.
The benefits of using software design patterns
Modern software development is largely based on the correct use of appropriate tools and frameworks. Many of the patterns are hidden in frameworks, and developers use patterns even without realizing it. So why should developers spend time learning about patterns? Let’s look at some benefits:
- Simplified development: due to design patterns being based on the knowledge and experience of experienced developers, patterns are proven and effective solutions.
- Reusable software architecture: across projects, software design patterns provide transparency and cleanliness to the app’s design, which, in turn, provides the ability to reuse software design patterns on different projects.
- Rapid and easy documentation: design templates are documented in a format that does not need to be tied to a specific problem.
- Interface inheritance (particularly for C#, Java, and .NET developers): the strength of inheritance is that you can use the code of a base class in a derived class without having to rewrite it.
- Versatility: software design patterns are not limited to any single programming language, making them highly useful.
The drawbacks and criticism of using software design patterns
If you think critically about patterns before software development, you can, to some extent, save time and reduce wasted effort and make a better application. It's hard to imagine that using software design patterns in software development may have any drawbacks. Nevertheless, here are the most typical arguments against using patterns:
- Irrelevant use: many developers implement design patterns everywhere without adapting them to the context of their project, which does not produce the expected results.
- Excessive use: once they learn about software design patterns, developers, especially beginners, try to use them everywhere, even in situations where simpler code can be handled. In this case, the complexity of writing code only increases.
- Lack of new solutions: design patterns can also lead developers to believe that all problems can be solved with existing design patterns. This can limit creativity and the desire to find new or better solutions.
Even though software design patterns are an essential part of any developer's toolkit, it is important to remember that software design patterns are no substitute for real-world problem-solving capabilities in software development.
In Android development, patterns are an integral part of the development process. Some of them have penetrated Android development so much that in most cases developers, especially beginners who are not familiar with patterns, do not even notice that they are using them. The most frequently used patterns are Observer, Singleton, Builder, and Adapter and in my opinion, it is quite difficult to imagine the development of an Android application without using them.
Bogdan Stolyarov, Android Developer at SoftTeco
I tried to study software design patterns myself, but the ones that I found were for the code written in object-oriented style, while I use functional style. So they seemed quite complicated to me back then, especially considering the fact I had no experience in using them. However, now I understand that they can be used in functional programming as well, but in a slightly different way.
I would probably add from my own experience that it's better to start coding without using software design patterns because without enough experience you can make the code much more complicated and will get used to adding them whenever you face difficulties in reusing your own or someone else's code.
Oleg Konan, Frontend Web Developer at SoftTeco