What is design pattern

Design pattern is a set of conclusive solutions to those frequently appeared problems.

Why design pattern

The design patterns help you to write flexible, low-coupled, high-cohesive code.

How to learn design patterns

In stead of think design pattern as a technical thing, try to think it as art. Actually it is art.

Learn design pattern in following ways
1. Motivation(what is cons of not using this pattern, real use case as example)

2. Implementation(how to implement pattern in code level)

3. Pros and cons

4. Pattern correlations(how patterns are similar to each other, and how patterns can work together)

Types of design pattern

There are three types of design patterns:

1. Creational Design Pattern
   1. Creational Design Pattern is used for initializing object. They gives you a lot of flexibility to control how/when/what object is created.
2. Structural Design Pattern
   1. Give people a better reasons to do modularization.
   2. Structural Design Pattern is a set of solutions of how to composite and arrange classes together to have better flexibility to fix with each other and to be extended.
3. Behavioral Design Pattern
   1. Behavioral Design Pattern is a set of design patterns that decide how the responsibility is assigned between different classes, as well as how different classes can talk to each other. Therefore, we can build a really complex system with a lot of simple classes.

Motivation

Considering that you are facing this situation: you built a

Definiton

Implementation

Pros & Cons

Use Cases

Decouple client and subsystem

adheres to the Principle of Least Knowledge,

Abstraction of the interface? Yes