As software engineers, we all should already know that, when working on a new project, you start by establishing the way of attacking-solving the problem or software to develop. So it is important to get there are these things called patterns (software design patterns) which may help you as a guide to your way of working.
A design pattern is a general repeatable solution to a commonly occurring problem in software design. A design pattern isn’t a finished design that can be transformed directly into code. It is a description or template for how to solve a problem that can be used in many different situations.
There are three design patterns we are going to talk about.
Structural
In Software Engineering, Structural Design Patterns are Design Patterns that ease the design by identifying a simple way to realize relationships between entities, making it easier for these to work together.
- Adapter
Match interfaces of different classes - Bridge
Separates an object’s interface from its implementation - Composite
A tree structure of simple and composite objects - Decorator
Add responsibilities to objects dynamically - Facade
A single class that represents an entire subsystem - Flyweight
A fine-grained instance used for efficient sharing -
Private Class Data
Restricts accessor/mutator access
- Proxy
An object representing another object
Creational
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.
- Abstract Factory
Creates an instance of several families of classes - Builder
Separates object construction from its representation - Factory Method
Creates an instance of several derived classes - Object Pool
Avoid expensive acquisition and release of resources by recycling objects are no longer in use - Prototype
A fully initialized instance to be copied or cloned - Singleton
A class of which only a single instance can exist
& finally
Behavioral
These design patterns are all about Class’s objects communication. Behavioral patterns are those patterns that are most specifically concerned with communication between objects.
- Chain of responsibility
A way of passing a request between a chain of objects - Command
Encapsulate a command request as an object - Interpreter
A way to include language elements in a program - Iterator
Sequentially access the elements of a collection - Mediator
Defines simplified communication between classes - Memento
Capture and restore an object’s internal state - Null Object
Designed to act as a default value of an object - Observer
A way of notifying change to a number of classes -
State
Alter an object’s behavior when its state changes
- Strategy
Encapsulates an algorithm inside a class - Template method
Defer the exact steps of an algorithm to a subclass - Visitor
Defines a new operation to a class without change
If you are a more listener boy, girl or apache helicopter, then you should watch-listen this video
Source: https://sourcemaking.com/design_patterns