Design Patterns

Design patterns provide general solutions to software design problems we find in real-world application development.

Before starting with design patterns let's understand what the meaning of design patterns and why they are useful in software programming/architecture.

"Each pattern describes a problem that occurs over and over again in our environment, and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over, without ever doing it the same way twice." - Christopher Alexander, A Pattern Language.

It is important to understand design patterns rather than memorizing their classes, methods and properties. First identify the software design problem then see how to address these problems using design patterns and determine the best suited design problem to solve the problem.

There are 23 design patterns, also known as Gang of Four (GoF) design patterns. The Gang of Four are the authors of the book, "Design Patterns: Elements of Reusable Object Oriented Software".

Creational Design Pattern

In software engineering, creational design patterns are design patterns that deal with object creation mechanisms, trying to create objects in a manner suitable to the situation. The basic form of object creation could result in design problems or added complexity to the design. Creational design patterns solve this problem by somehow controlling this object creation.

Factory Method

The factory method pattern is a creational pattern that uses factory methods to deal with the problem of creating objects without having to specify the exact class of the object that will be created. This is done by creating objects by calling a factory method—either specified in an interface and implemented by child classes, or implemented in a base class and optionally overridden by derived classes—rather than by calling a constructor.

Builder

The Builder is a design pattern designed to provide a flexible solution to various object creation problems in object-oriented programming. The intent of the Builder design pattern is to separate the construction of a complex object from its representation.

Singleton

The singleton pattern is a software design pattern that restricts the instantiation of a class to one single instance. This is useful when exactly one object is needed to coordinate actions across the system.