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No constructors, no static methods, no operators
No type declaration, no primitive types,
No interfaces, no need for factory
No packages/private/protected modifiers
No parametrized types
No boxing/unboxing
Still powerful
A Pure OO World
Only objects mouse, booleans, arrays, numbers, strings, windows, scrollbars, canvas, files, trees, compilers, sound, url, socket, fonts, text, collections, stack, shortcut, streams, …
& messages
Simple and Uniform
Everything in an object instance of a class
Classes are objects
Only message passing (method invocation)
Only one method lookup (virtual)
Packages contain classes and methods
Object Model
Instance variables are private to the object (instance-based)
ClassVariables are shared between subclasses
Instance variables are protected
Methods are public, virtual
Single Inheritance
Object subclass: #Point
instanceVariableNames: 'x y'
classVariableNames: ''
category: 'Graphics-Primitives'
Single Inheritance
Messages + Objects
Object
Node
accept:
name
sendt:
node1
msg
The key to everything
Look for the message selector in the class of the receiver
if found return it
if not look in the superclass
Execute the message on the receiver
Sending a message
!
Point selectors
!
> an IdentitySet(#eightNeighbors #+ #isZero #sortsBefore: #degrees #printOn: #sideOf: #fourNeighbors #hash #roundUpTo: #min: #min:max: #max #adaptToCollection:andSend: #quadrantOf: #crossProduct: #= #nearestPointOnLineFrom:to: #bitShiftPoint: #* #guarded #insideTriangle:with:with: #grid: #truncateTo: #y #setR:degrees: #normal
Classes are objects too
!
Point instVarNames
Classes are objects too
!
Point instVarNames
>#('x' 'y')
Classes are objects too
Instance creation
Just messages send to special objects that are classes
Morph new
Character cr
Rectangle origin: 0@0 corner: 100@200
Tomagashi withHunger: 10
Class methods are plain late bound methods as any methods!
Cheap factories :)
Cheap factories :)
Parser>>parse: line
self sortedParsers
detect: [ :sub | (sub canParse: aLine)
ifTrue: [ ^ sub newFromLine: line ] ]
!
Parser>>sortedParsers
^ DocumentItem allSubclasses
sorted: [ :c1 :c2 | c1 priority < c2 priority ]
!
!
Classes are objects too
!
Point class
Classes are objects too
!
Point class
>Point class
!
Classes are objects too
!
Point class
>Point class
!
“Point class” is an anonymous class (called a metaclass) with only one instance: the class Point
Classes are objects too
Class Parallel Inheritance Node class
newwithName: aString
instance of
Node
nameaccept: aPacketsend: aPacket
Workstation
originate: aPacketaccept: aPacket
aWorkstation (BigMac)
Workstation
class
instance of
Lookup and Class Methods
About the Buttons
Package extensions
A method can be defined in a class that is packaged in another package! Powerful to build layers
Defined in the Dice package Integer>>D20 ^ self D: 20 !
Integer>>D: anInteger | h | h := DiceHandle new self timesRepeat: [h addDice: (Dice faces: anInteger)]. ^ h
2 D20: two dice of 20 faces
SummaryEverything is an object
Single inheritance, public methods, protected attributes
One single model
Classes are simply objects too
A class is instance of another class
One unique method lookup, look in the class of the receiver
A package can contain methods defined on classes defined in other packages.
