Undo History with Flight
Change the Past.

Intoduction
Tyler Wright – www.xtyler.com
Flight Framework – www.flightxd.com
Robert Taylor – www.roboncode.com
Jacob Wright – jacwright.com
Resources: www.xtyler.com/history

Ctrl+Z
Desktop Applications
Browser TextFields
What about Rich Internet Applications?
Users can enjoy making mistakes

Flight Framework
an application framework
an undo framework
a command factory
a data binding fiend
a way to get dates

Anatomy of Undo
Undoable Action
means of reverting that action
recover from a single mistake
Memory of actions
queue of undoable actions
recover from a history of mistakes
Change the past.

Anatomy of Undo
• Undoable Action
• Action Memory

Generic vs. Specific
One-size fits all Everyone is special
“automatic” custom
centralized logic handles separate logic for undo on
undo on all actions each action
actions must fit the mold every action unique

Command your Actions
Methods define our system’s actions
State is represented by local data – goes away
Command: an objectified method, storing local data
Portable – pass around the system as an object

Implement to an Interface
Interfaces: create types by contract
ICommand
execute():void
IUndoableCommand
undo():void
redo():void

CommandHistory
Undo & Redo “right out of the box”
ICommandInvoker
executeCommand(command:ICommand):void
ICommandHistory
canUndo():Boolean, canRedo():Boolean
undo():Boolean, redo():Boolean
undoLimit:int, etc…

Action Memory Realized
Commands become our undoable actions
CommandHistory becomes our memory of actions

Generic heart Specific
One-size fits all Everyone is speaical
“automatic” custom
single command to a separate Command for
represent all actions each action
Marriage by Command
Consolidates these approaches.
Provides a single interface to undo and redo.
Mix approaches or migrate from one to another without changing API.

Your First History Lesson
The History Panel
Photoshop
Flash
The Project
(break to code right here)
On Into the Details

Short-term Memory
Undo limits
Considering stored data
types
Clearing memory –
release event listeners and
bindings
Weak-referenced event
listeners and binding
Saving history to disk

Merging
Actions repeated
IMergingCommand
merge (source:Object):Boolean
Originating Command inspects fellows before
discarding them – self reflection leads to a greater self
Compared to MacroCommands

Flight Framework Reloaded
Offers the HistoryController as an extension of application-
level Controllers
Command Factory
addCommand(type:String, commandClass:Class):void
createCommand(type:String):ICommand
Enables direct upgrade from a common application to one
with undo and redo, minimal changes
Much more…

Change the Past.
Tyler Wright – www.xtyler.com
Flight Framework – www.flightxd.com
Robert Taylor – www.roboncode.com
Jacob Wright – jacwright.com
Resources: www.xtyler.com/history