"Actionscript 3.0 Design Patterns" - Joey Lott

An eagerly awaited session as Joey has basically written the book(s) on ActionScript. I was surprised by how young he was. Cool jersey by the way Joey!

• This session won't be entertaining or funny. It will be dry, we'll cover a lot of ground and there'll be a lot of code in it.


• What are design patterns?
  
  
  • Elegant solutions to common problems
  
  
  • Guidelines
  
  
  • Shared language


• Why use design patterns?
  
  
  • Don't reinvent the wheel
  
  
  • Work smarter and faster
  
  
  • Communicate more efficiently


• "Design Patterns: Elements of Reusable Design" - recommended book as a starting place for design patterns


• Pitfalls of using Design Patterns
  
  
  • Designpatternitis
    
    
    • Turning apps into design pattern stew
    
    
    • Using patterns inappropriately for the sake of it
  
  
  • Over-complication
  
  
  • Inflexibility


• Important Fundamentals of Design Patterns
  
  
  • Programming to an interface/polymorphism
  
  
  • Understanding abstract classes
  
  
  • Using inheritance and composition
  
  
  • Architecture 101
    
    
    • Discreet groupings
    
    
    • Keep to 1-3 responsibilities for a class


• 1. MVC - Model Viewer Control pattern
  
  
  • Remove data from representation of the data and again from the control of the data
  
  
  • Model - just store data
  
  
  • View - displays it
  
  
  • Control - allows different views


• 2. Singleton pattern
  
  
  • One managed instance of a class in your app
  
  
  • Creating it as a public static and gets it from class using public static method
  
  
  • Constructor never called from outside class
  
  
  • Can force this using an internal "enforcer" class


• 3. Iterator
  
  
  • Puts all the iterative processing behind an interface to force a it be done the same way - forces a common language
  
  
  • So if you want to do something different (i.e. get stuff in reverse) create a new iterator which also uses the interface so commands called are all the same
  
  
  • Iterator can then be swapped out at runtime without breaking!


• 4. Command
  
  
  • Similar but for commands
  
  
  • E.g.
    
    
    • ICommand - execute()
    
    
    • IRedoableCommand - redo()
    
    
    • IUndoableCommand - undo()
  
  
  • Keep history (call stack of instances) and just call undo() in each - simple and easy!


• 5. Memento
  
  
  • Missed most of this as dropped my pen and spent most of the time on the floor looking for it - eventually remember another one in my coat pocket!
  
  
  • Made up of...
    
    
    • Originator
    
    
    • Caretaker
    
    
    • Memento
  
  
  • E.g.
    
    
    • Memento tells radius and colour of circle
    
    
    • Originator - creates circle object and gets rad and col from the memento
    
    
    • Caretaker - main class, instantiates the originator with the memento values
  
  
  • This is a bit muddled because of the pen incident


• 6. Decorator
  
  
  • Allows permutations
  
  
  • Put decorators on the top of each other to keep extending them
  
  
  • Decorators can be a direct inheritance or creating using an abstract class in a real object and passing it into different decorators and getting a modified one in return (this sounds a bit muddled but his example was ace)
    
    
    • Shape (abstract) > Circle (shape) > Blue (deco) > Bevel (deco) > Size (deco)
    
    
    • MyBevel = new BevelClass(myShape);
  
  
  • His book sounds good: "Advanced ActionScript 3 with Design Patterns"