Design patterns

Design patterns are general solutions to common software design problems. They're not specific to any one programming language or framework, which makes them handy tools to have in your toolkit. When you're approaching a system design problem during an interview, being able to quickly identify which design pattern would be the best fit can save you a lot of time and impress your interviewer.

Why Are They Important?

There are three main reasons why design patterns are so important: 

They're battle-tested

Design patterns have been used in production by experienced developers for years. This means that they've been proven to work effectively in solving real-world problems. 

They're easy to remember

The fact that design patterns are abstract solutions means that they're easy to remember and apply to new problems. 

They help you communicate with other developers

Because design patterns are so well-known in the industry, using them in your conversation with other developers will help ensure that everybody is on the same page. 

Now that we know what design patterns are and why they're so important, let's take a look at some of the most popular ones. 

The Singleton Pattern

The singleton pattern is one of the most well-known design patterns. It is used to ensure that only one instance of a class is created. This is useful in situations where global variables need to be accessed from multiple places in the code. 

The singleton pattern can be implemented in two ways: lazy initialization and eager initialization. Lazy initialization means that the instance of the class is only created when it is first needed. Eager initialization means that the instance is created when the class is loaded.   Pacers use lazy initialization while WellFurnished uses eager initialization. 

The Factory Pattern

 The factory pattern is another very popular design pattern. It is used to create objects without having to specify their exact type. This is useful in situations where the exact type of object that needs to be created is not known beforehand.   There are three types of factories: abstract factories, concrete factories, and static factories. Abstract factories return different types of objects depending on their input. Concrete factories return objects of a specific type. Static factories return objects without using an object instantiation (such as by using a static method). 

The Builder Pattern 

 The builder pattern is used to create complex objects with many parts." It is similar to the factory pattern, but it allows for finer control over the construction process. 

 The builder pattern has four parts: the builder interface, the concrete builder, the director, and the product." The builder interface defines methods for creating the different parts of an object. The concrete builder implements methods from the builder interface to create an object according to specifications from a director. The director tells the builder what needs to be built and controls the construction process." The product is the object that is being built by the builder."