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Object Oriented Design Cheat Sheet by

A handy guide to the basic principles of Object Oriented Programming and Design. Covers standard and accepted principles, design patterns, and more! This is not intended to teach OOP, but as a reminder for those who already learned.

SOLID

Single Respon­sib­ility Principle
A class changes for only one reason
Open/Closed Principle
A class should be open for extension, closed for editing
Liskov's Substi­tution Principle
Derived types should cleanly and easily replace base types
Interface Segreg­ation Principle
Favor multiple single­-pu­rpose interfaces over composite
Dependency Inversion Principle
Concrete classes depend on abstra­ctions, not vice-versa

Other Principles

Don't Repeat Yourself (DRY)
Duplic­ation should be abstracted
Law of Demeter
Only talk to related classes
Hollywood Principle
"­Don't call us, we'll call you"
You Ain't Gonna Need It
Only code what you need now
Keep It Simple, Stupid
Favor clarity over cleverness
Convention Over Config­uration
Defaults cover 90% of uses
Encaps­ulation
What happens in Vegas...
Design By Contract
And then write tests
Avoid Fragile Base Class
Treat Base like a public API
Common Closure Principle
Classes that change together, stay together

Common Refact­orings

Encaps­ulate Field
Generalize Type
Type-C­hecking ⇒ State/­Str­ategy
Condit­ional ⇒ Polymo­rphism
Extract Method
Extract Class
Move/R­ename Method or Field
Move to Superc­las­s/S­ubclass
 

Class Associ­ations: Associ­ation

Two objects have some sort of relati­onship to each other.
Example: Car uses Highway

Class Associ­ations: Aggreg­ation

An associ­ation where one object has-a (owns a) different object.
Example: Car has a Driver

Class Associ­ations: Compos­ition

An aggreg­ation with dependency - objects are mutually destro­yed­/cr­eated.
Example: Car has an Engine

Class Associ­ations: Genera­liz­ation

"­Is-­A" relati­onship (inher­ita­nce).
Example: Porsche is a Car

Class Associ­ations: Realiz­ation

One class implements behavior that is abstractly defined in another class.
Example: An Animal may Move(), but a Duck would move by waddling

Class Associ­ations: Dependency

One class weakly depends on another.
Example: Car uses Highway
  

Access Modifiers

Private
Only inside the same class instance
Protected
Inside same or derived class instances
Public
All other classes linkin­g/r­efe­rencing the class
Internal
Only other classes in the same assembly
Protected Internal
All classes in same assembly, or derived classes in other assembly
Static
Accessible on the class itself (can combine with other accessors)

Design Patterns (GoF)

Abstract Factory
Creational
Builder
Creational
Factory Method
Creational
Prototype
Creational
Singleton
Creational
Adapter
Structural
Bridge
Structural
Composite
Structural
Decorator
Structural
Facade
Structural
Flyweight
Structural
Proxy
Structural
Chain of Respon­sib­ility
Behavioral
Command
Behavioral
Interp­reter
Behavioral
Iterator
Behavioral
Mediator
Behavioral
Memento
Behavioral
Observer
Behavioral
State
Behavioral
Strategy
Behavioral
Template Method
Behavioral
Visitor
Behavioral
           
 

Metadata

  • Languages:
  • Published: 9th January, 2012
  • Last Updated: 13th May, 2016
  • Rated: 5 out of 5 stars based on 46 ratings

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Comments

thank you so much - this is perfect!

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