‘Design Pattern’ is a familiar term for software engineers. Design patterns are predefined rules primarily applied in a code to solve a problem. Since software developers are never short of problems to solve, it makes sense to follow a set of instructions defined by elite software engineers. Especially if it’s a new type of problem they have to solve. Top software engineers have created a rich repository of design patterns. Although they address various features, most design patterns fall into three fundamental types.
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Creational design patterns focus on class instantiation or the creation of an object. This pattern uses inheritance for either creating a class or an object of that class. For example, consider this scenario:
A database connection is created to access data. Developers usually make a connection every time they access data in different locations of the code. Although syntactically correct, this practice is not necessary. It can even cause problems in the code. The data can even be overwritten if modifications are later made in the code. The industry’s elite talent foresaw these problems early on. And introduced design patterns in response.
Singleton, a creational type of design pattern, solves the problem described above. It instructs the developer to create a single DB connection class. Whenever the data exchange is required, an instance of that class will be called. A single connection will be established by this and all other connections can be avoided. This concept of creating a single class has many other applications as well.
The Factory Method, Abstract Factory and Builder are other examples of creational patterns.
Structural design patterns are based on organizing and managing different classes and objects in a proper structure. Structural design patterns reduce incompatibility between components. Thus, making the components work together to produce the functionality needed. Adapter, Bridge and Composite are some structural design patterns.
These patterns refer to the behavior of communication patterns between components of the code.Behavioral patterns use the communication between components as a feature to increase usability and expansion in the program. For instance, using ‘Template’, (a behavioral design pattern), a program can be designed such that it gives rights for adding any new features or functionality in the program. It does this by extending a module. The user will not be able to access the core functionality of the program. Nor will he/she be able to change any prewritten code. This application of the Template Pattern/Code—which makes sub-classes public and accessible, but keeps the core classes private, (and thus inaccessible by some users) has many uses.Some other behavioral patterns are Command, Interpreter, Iterator, Mediator, Memento, Null Object, and Observer.
Design patterns offer many advantages: Code becomes robust, easy to read and reuse. That’s because design patterns address two programming fundamentals: Coupling and cohesion.
Coupling refers to the dependency of software components on each other. How:
High coupling results in very complex code. It can be difficult to maintain such code, thereby reducing its usability. A minor problem in one component can disturb other components as well.
Low coupling signifies good code structure. It makes code robust, as the impact of any component’s modification is low on other components.
Reducing coupling is quite difficult and can change the entire code. Design patterns define the rules and methods that can solve such issues. Software developers can minimize coupling by following a design pattern from the start.
Cohesion measures how well a code component has been built. And how well it focuses on a specific task. According to encapsulation (a fundamental object-oriented design principle), all the related data and its functions should be encapsulated in a class. This ensures all related functionalities are in one location, and their accessibility can be controlled.
Low cohesion indicates that a class is performing several jobs and is not focused. High cohesion is better and shows that a class is performing a well-defined job. The following is an example of code with low cohesion and tight coupling:
class Service { public Register RegisterPerson( ) { //logic } public Job AssignJob( ) { //logic } public Office AssignOffice( ){ //logic } }
To make the code above more cohesive, we give each class a focused job. We separate the tasks performed by each class for specificity. Now the following is an example of high cohesion and loose coupling in code:
class Service { public Register RegisterPerson( ){ //logic } } class Assignments { public Job AssignJob( ){ //logic } public Office AssignOffice( ){ //logic } }
Design patterns also offer advantages in testing. Typically, testing is conducted by different groups of software engineers. Testers can easily understand the flow of code. That is, if they know which design pattern was used during the implementation. They can foresee fails based on previous experiences with design patterns. And thus, perform the most relevant testing.
A strong understanding of design patterns also helps with communication and support. There are many popular design patterns discussed in software developer communities and forums. Developers facing issues can get help from other skilled software developers.
Elite talent is often challenged in describing its work to non-technical professionals. Design patterns help bring everyone on to the same page. During discussions, merely referring to the patterns enables software developers to visualize requirements.
IT recruiters recognize the importance of using design patterns. For many, the ability to use design patterns correctly signals top talent. (And high potential) in the technology industry. Many onsite development companies use design patterns in all their projects, creating commonality across the modules. This practice also removes the variability that may exist in system requirements. This explains why IT recruiters seek software developers with extensive knowledge of design patterns.
The best tech talent uses design patterns extensively. And encourages beginners to use them too. These patterns can help programmers in applying their programming knowledge accurately and more extensively. Having said that, design patterns are not a static programming philosophy. They are constantly evolving to offer the best solutions to repetitive software development problems. Want to learn the insider angle of software development and structure? Design patterns offer the easiest start.
Shaharyar Lalani is a developer with a strong interest in business analysis, project management, and UX design. He writes and teaches extensively on themes current in the world of web and app development, especially in Java technology.
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