This document provides an overview of object-oriented programming concepts and the Smalltalk programming language. It discusses the essence of class-based object orientation, including classes, objects, encapsulation, inheritance and polymorphism. It then introduces the Smalltalk language, covering its history and development, core concepts like everything is an object and message passing, and how to get started programming in Smalltalk. Standard development tools and syntax like methods, statements, control structures and creating classes are also summarized.

1. Object-oriented
!quot;#$
programming in
Smalltalk
Alexandre Bergel
RMoD team, INRIA,
Lille, France
alexandre@bergel.eu

2. Goal of this lecture
• Gain elementary notions of object orientation
• Learn what is a pure object oriented language
• Increase the programming language section on your CV

3. Outline
1. Essence of class-based object orientation
2. Object oriented programming with Smalltalk
3. Smalltalk in Action

4. Outline
1. Essence of class-based object orientation
2. Object oriented programming with Smalltalk
3. Smalltalk in Action

5. Procedural programming
color = data
shape = behavior
(Flatt 98)

6. Procedural programming
(Flatt 98)

7. Expressing combination

8. Example in C
struct Point { struct Circle {
const void * class; const void * class;
int x, y; int x, y, rad;
}; };
void draw (void * self) { void move (void * self) {
switch(self[0]) { switch(self[0]) {
case POINT_CLASS: ... case POINT_CLASS: ...
case CIRCLE_CLASS: ... case CIRCLE_CLASS: ...
} }
} }
!quot;#$

9. Expressing extension

10. Expressing extension

11. Situation with some difficulties

12. Object-oriented programming
• Simula 67 addressed the combinational explosion of data
and behavior
• a class is an object factory
• class = superclass + attributes + methods
• object reactive to messages

13. Object as programming entities
a student
printDescription() name=Bill
courses={c1, c2}

14. Object as programming entities
^ 'My name is ',
Person name
age
gender
description()
Transcript show:
printDescription()
self description
a student
Student
printDescription() name=Bill instance courses super description,
courses={c1, c2} description() ' and I follows ',
courses

15. Object as programming entities
^ 'My name is ',
Person name
age
gender
description()
Transcript show:
printDescription()
self description
a student 1
Student
printDescription() name=Bill instance courses super description,
courses={c1, c2} description() ' and I follows ',
courses

16. Object as programming entities
^ 'My name is ',
Person name
age
gender
description()
Transcript show:
printDescription()
self description
a student 1
Student
description() name=Bill instance courses super description,
courses={c1, c2} description() ' and I follows ',
courses
2

17. Object as programming entities
3
^ 'My name is ',
Person name
age
gender
description()
Transcript show:
printDescription()
self description
a student 1
Student
super name=Bill instance courses super description,
description()
courses={c1, c2} description() ' and I follows ',
courses
2

18. Object as programming entities
3
^ 'My name is ',
Person name
age
gender
description()
Transcript show:
printDescription()
self description
a student 1
Student
super name=Bill instance courses super description,
description()
courses={c1, c2} description() ' and I follows ',
courses
2

19. Object-oriented programming
Encapsulation Abstraction & Information Hiding
Composition Nested Objects
Distribution of Separation of concerns
(e.g., HTML, CSS)
Responsibility
Message Passing Delegating responsibility
Conceptual hierarchy,
Inheritance polymorphism and reuse

20. Outline
1. Essence of class-based object orientation
2. Object oriented programming with Smalltalk
3. Smalltalk in Action

21. Smalltalk

22. The origin of Smalltalk
Alan Kay’s Dynabook project (1968)
Alto — Xerox PARC (1973)

23. Smalltalk today

24. Smalltalk today

25. Smalltalk today

26. Smalltalk today

27. Smalltalk today

28. Squeak resources
www.squeak.org www.seaside.st
Downloads and links One-click image
SqueakByExample.org
Free download — Print-on-demand

29. Getting started

30. Everything is an object

31. Everything happens by sending
messages

32. Running Squeak

33. Do it, print it
You can evaluate any
expression anywhere
in Smalltalk

34. Standard development tools

35. Debuggers, Inspectors, Explorers

36. Syntax in a Nutshell

37. Three kind of messages
5 factorial
Unary messages Transcript cr
Binary messages 3 + 4
Keyword messages
3 raisedTo: 10 modulo: 5
Transcript show: 'hello world'

38. A typical method in the class Point
Method name Argument Comment
<= aPoint
quot;Answer whether the receiver is neither
below nor to the right of aPoint.quot;
^ x <= aPoint x and: [y <= aPoint y]
Return Binary message Block
Instance variable Keyword message
(2@3) <= (5@6) true

39. Statements and cascades
Temporary variables
Statement
| p pen |
p := 100@100.
pen := Pen new.
pen up.
pen goto: p; down; goto: p+p
Cascade

40. Control structures
Every control structure is realized by message sends
4 timesRepeat: [Beeper beep]
max: aNumber
^ self < aNumber
ifTrue: [aNumber]
ifFalse: [self]

41. Control structures
Every control structure is realized by message sends
4 timesRepeat: [Beeper beep]
Boolean
ifTrue:ifFalse:
max: aNumber True False
^ self < aNumber ifTrue:ifFalse: ifTrue:ifFalse:
ifTrue: [aNumber]
ifFalse: [self]
ifTrue: t ifFalse: f ifTrue: t ifFalse: f
^ t value ^ f value

42. Creating classes
Send a message to a class (!)
Number subclass: #Complex
instanceVariableNames: 'real imaginary'
classVariableNames: ''
poolDictionaries: ''
category: 'ComplexNumbers'

43. Outline
1. Essence of class-based object orientation
2. Object oriented programming with Smalltalk
3. Smalltalk in Action