How To

Think

Like a

Programmer

Part 4: Design Patterns

By @ErikRalston

Design Pattern

A reusable concept for structuring code

A writing "cliche" for code

Programming Paradigm

Procedural Programming

Code and Data are Separate

Code is broken into functions

Code is pages (files) of paragraphs (functions)

Object-oriented Programming

Code and Data Organized Together

Code becomes characters with defined abilities (Object)

Or each Object could be thought of as its own book

Principles of oOp

Encapsulation

Bundling of data with behavior, exposing only necessary data

Abstraction

Simplify the program by hiding state

Inheritance

Reuse functionality by

oo style #1: classes

Each object is a Type of object

They belong to a "Class"

Traits are genetic

Types can have child types that "inherit" their abilities

C++, Java, C#

OO Style #2: prototypes

Each object refers to a parent "Prototype" object

Anything requested by

Traits are Contextual

JavaScript

object-oriented

design patterns

Strategy pattern

Implement a different algorithms for related problems

Each in different sub-class

Singleton Pattern

Maintain only a single instance of an object

Grants access across the program to a necessary resource

factory Pattern

Instead of objects making themselves

Have an object make one for you

command pattern

Make an object for each action with a system

Enables extension of the system without altering it

Visitor Pattern

For a collection of objects

Place logic in something that visits them

Instead of the collection itself

Singleton Pattern

Maintain only a single instance of an object

Composite Pattern

Make a sub-class that is a collection of the class

Applying actions to all children

hands-On

Designing Photoshop