Smalltalk and pure object oriented programming
OO Focuses on the Data
Pure Object-Orientation: Everything is an object
More about objects
What is a class?
Classes are also objects!
Example
Diagram of Ball class and its instances
Everything is an object!
is-instance-of relationship
is-a relationship
Object hierarchy
Computation via messages and methods
Object-oriented vs. procedural terminology
Smalltalk-80
Features of Smalltalk-80
Smalltalk Class Browser
Class Hierarchy Pane The Class Hierarchy Navigator
Variables Pane A Filter for the Methods Pane
Methods Pane A Listing of the Relevant Methods
Method Definition Window
So where’s my program?
Filing out your code
Filing in code
Asking questions about code
Learning more about Smalltalk/Express Environment
Simple Smalltalk Syntax
More Smalltalk Syntax
Stack Object Implementing a Stack ADT
Stack Object Methods
Adding a subclass
Adding a class method
Adding an instance method
More stack methods
Shared Variables
Private variables
Variables
Constructing a Stack
Object construction in Smalltalk
Initializer method
Common mistakes
Errors…
Superb Debugger!
Message terminology
Three kinds of Messages
Parsing Messages
Parsing keyword messages
The importance of the colon:
Cascading messages
Message dispatch
Dispatch examples
Method terminology
Dispatch algorithm
Talking to yourself
Smalltalk schizophrenia
Writing draw without message dispatch
So what’s the big deal?
Modularity
Overriding a method
Replacing a method
A less drastic change in behaviour
Do not duplicate code!
Getting help from your parent
super keyword
Example of super
Sample message sends
A small change
More message sends
Recursion
Conditionals
Blocks ? Scheme’s lambda
Blocks package up code
Class Boolean
Class Boolean has no state!
While loops
Common mistakes
Collection classes
Collections understand lots of messages...
do: and collect: messages
Dictionary class
The Smalltalk object
Smalltalk summary