Student Originated Software 1997-1998
Fall Quarter

A Software Engineering Course at
The Evergreen State College

ARCHIVE -

Student Originated Software 1997-8

Object-Oriented Programming (Smalltalk)

Lecture 2b

last time in class:

---------

block - a deferred sequence of messages

evaluated when the block receives the message

aBlock := [a:=0].

aBlock value

MyBlock := [:anObject | anObject print].

anotherBlock := [:parm1 :parm2| |tmp|

tmp := parm1 incorporate: parm2.

tmp := rehash.

]

executing blocks

MyBlock value: 'This is a string sent to print'.

value, value:, value:value:, value:value:value:

valueWithArguments:argArray (> 3 arguments.

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the smalltalk virtual machine (oe20)-- interprets code as it comes in

  • "the image" -- where code and object instances are stored

  • the Smalltalk Virtual Machine (your image is its memory)

  • the development environment (your classes + class library)

  • files - virtual image

  • sources visual.sources

  • (base) image visual.im

  • (your) image myvisual.im

  • changes file mymods.changes

  • file-outs mysource.st

  • file-ins "

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Application Development Environment

  • the language, tools, the class library

  • launcher, main window (aka transcript)

  • workspace

  • system browser

  • class browser

  • inspector

  • (debug window)

  • The system browser!

    5 panes:

    class categories, classes, protocols, methods,

    workspace to type code

in Lab - last Tuesday, Chapters 6 & 7.

add a new method to an existing class (Number)

do a small application

some useful browsers and menu operations.....

hierarchy

implementors of...

users of...

cookbook

help

The Spending App --

new category, with classes & methods).

self new initialize

self new setInitialBalace:anAmount

^self new setInitialBalace:anAmount

setInitialBalance: anAmount

cashOnHand := anAmount.

expenditures := Dictionary new.

totalSpentOn: reason

(expenditures includesKey: reason)

ifTrue:[^expenditures at:reason]

ifFalse:[0]

spend:anAmount on:reason

expenditures

at: reason

put: (self totalSpentOn: reason) + anAmount.

cashOnHand := cashOnHand - anAmount.

printOn:aStream

super printOn:aStream.

aStream space.

aStream nextPutAll: 'balance:'

cashOnHand printOn: aStream.

expenditures keysAndValuesDo: [:reason :amount |

aStream cr.

reason printOn: aStream.

aStream tab.

amount printOn: aStream]

invoking the app:

| mySpendingHistory |

mySpendingHistory := SpendingHistory initialBalance: 60000.

mySpendingHistory spend: 1000 on: 'rent'.

mySpendingHistory spend: 500 on: 'food'.

mySpendingHistory spend: 100 on: 'vet'.

mySpendingHistory spend: 25000 on: 'new car'.

"inspect" mySpendingHistory

you can modify the collection from the inspector

"inspect" the Smalltalk dictionary.

-----------

saving your source code

file out as ... Spending.st

-------

using the file browser, 'spawning' a new (file) broswer

--------

OO Design Spec for the Spending App.

Like an ER diagram, but with methods!

Ch 7 - The System Transcript

Transcript refers to an instance of TextCollector

show: aString

cr

tab

Object

printString

returns a string with a printable representation of the receiving object

implemented using printOn:, which is redefined in subclasses of Object.

Transcript show: (2 raisedTo:10) printString.

>>>How does Smalltalk decide which method to invoke when I send a message, since there are several methods of the same name?

Transcript cr. Transcript tab. Transcript show: 'String on a new line'; cr.

Transcript show: (3+4) printString; cr.

Transcript show: (22/7) printString; cr.

Transcript show: (42 raisedTo: 42) printString; cr.

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Chapter 8 - Class Point.....

information hiding

encapsulation

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Chapter 9 - Other kinds of Browsers

class browser

hierarchy browser

spawn hierarchy

Beware of changing classes w/ multiple browsers open!

use update!

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Assignment for Next week

Inheritance, class variables and abstract superclasses.

So far, it looks like we might be able to stick with the syllabus.

How's the pace?

- Tuesday - Asst (due) - Read Ch.11,12, 13.

Programming Assignment....


due: Tuesday (or Thursday ???)

Turn in Exercise 10.1, 10.4, 10.6, 10.7, and 10.10. You may work on these exercises with a group, but please write them up with at most one other person. Two persons may turn in one programming assignment.

- Thursday - Unordered Collections. Asst (due) - Read Ch. 14.

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Created by: SoSwEbGrOuP
E-mail: ringert@evergreen.edu