A Deep Dive into 9 Popular Design Patterns and Their Uses

A Deep Dive into 9 Popular Design Patterns and Their Uses

Whether you’re working on simple software components or complex architectural structures, chances are you’ll come across and use design patterns. As we’ve previously explored on this blog, design patterns are essentially a reusable solution to a commonly occurring problem within a given context in software design. Zooming in a little closer, we can say it’s a blueprint or recipe for how to solve a problem that can (and should) be customized so that it can be applied in different contexts and situations. 

Design patterns are great time savers for software developers. After all, there’s no need to create a solution from scratch when there’s already one that has been tested thoroughly and is proven to work. Moreover, as these patterns are recurring, they become easily identifiable and make it easier for other developers to understand what’s going on in someone else’s code. As patterns have been fine-tuned over time, they are also likely to make your code more elegant and concise.

Of course, to take full advantage of the benefits of design patterns, you need to know which ones are available, why they are useful, and when they are suitable in practice. Before we look at the most popular patterns out there today, it’s crucial to remember that design patterns are not ‘one-size-fits-all’ shortcuts that can just be mindlessly copied into your code. Nor should they be seen as substitutes for problem-solving in software engineering. With that understood, let’s take a closer look at the most common design patterns used today across three broad categories: creational, structural and behavioral. 


Creational Patterns

These provide mechanisms to create objects in a controlled manner that are suitable to the situation. In this way, they help reduce complexities and instability, while also offering increased flexibility and allowing for the reuse of code. Some of the most popular examples are:

Singleton: A simple but powerful design pattern that limits a class to a single instance, while providing global access to this instance. A common real-life analogy is that of an office printer being shared by multiple employees - a single instance of the printer that everyone can access is more useful than creating new instances for each person that wants to print a document.

Factory Method: This pattern is for the (mass) production of objects without specifying their exact class - a bit like a real-world factory producing goods at scale. In the factory method, subclasses are typically responsible for creating the specific instance of the class. It’s useful when you don’t know beforehand the exact specificities and dependencies of the objects your code will be working with, allowing for the easy addition of subclasses to determine new instances. 

Constructor/Builder: This pattern is often used to simplify the construction of complex (or composite) objects with a step-by-step approach. One very basic way to think of it is likely making a pizza, where you have to start with the base, then add sauce, cheese, and then a range of toppings. At each stage, there are variables to consider: the thickness of the dough, the amount of sauce, the type of cheese, the different combinations of toppings. The constructor pattern organizes each of these simple steps to deliver the final product, with the ability to build different representations of the object (i.e. different types of pizza). 


Structural Patterns

These are concerned with assembling objects and classes into larger structures while keeping these structures flexible and efficient. They provide a manner to define relationships between the components of an application and are particularly useful in larger systems.

Adapter: This functions as a bridge between two incompatible interfaces. Think of an interpreter, sitting between two people having a conversation in different languages (a common problem in programming!), or a simple plug adapter that allows you to charge your US phone in any country. By enabling objects to communicate in a way that they both understand, the adapter pattern combines the capability of two independent interfaces.

Decorator: This pattern allows functionality to be added to an individual object without altering its basic structure. In other words, it is used to add an enhanced interface to the existing object - like adding lights and baubles to a christmas tree, or frosting and sprinkles to a donut. It allows developers to add behaviors and features to objects without changing source code. Just be cautious about adding too many layers and complexities to the original object.

Facade: As the name suggests, this pattern hides the complexities of a system from the client, providing instead a simple/attractive interface. The main advantage for developers comes through making complex software libraries or frameworks easier to understand and access. It can also isolate ‘outside’ code from the complex internal systems. 


Behavioral Patterns

These are in charge of ensuring effective communication between components. They are concerned with the interaction between objects, as well as the assignment of responsibilities. The goal is to make these processes as simple and understandable as possible. Important examples include:

Observer: When there is a one-to-many relationship between objects, this pattern ensures that all dependents ‘observe’ an object and will be immediately notified if anything happens to change its state. One real world example is when retailers or publishers inform subscribers about events that are of interest to them  (i.e. the release of a new item or an upcoming event).  

Strategy: This pattern lets you group related algorithms, put each of them into a separate class (‘strategies’), and make their objects interchangeable without modifying the client. In this way, a class behavior or its algorithm can be changed at run time, depending on the strategy selected. 

Chain of Responsibility: This pattern is used to pass client requests along a chain of objects (‘handlers’) to be processed. Each link in the chain will decide whether to process the request or pass it along to the next in line. One real-world analogy would be the operating system when you call your bank with a specific request - if none of the generic options in the automated system are relevant, you are connected with a customer service agent, who will either deal with your request or send you on to another department. 

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Feb 04, 2021
Santiago Castro
Santiago Castro

Santiago, COO at Jobsity, has been working on the web development industry for more than 15 years, assuming a variety of roles as UX/UI web designer, senior frontend developer, technical project manager and account manager, he has achieved a deep understanding of the development process and management, and developed strong communication skills with groups and clients. At present, Santiago runs the operations of Jobsity, managing offices in the United States, Ecuador and Colombia, leading a team of more than 100 developers, working on major projects for clients like NBC, GE, Bloomberg, Cargill, Pfizer, Disney and USA Today.



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