Student Originated Software 1997-1998 Fall Quarter
		A Software Engineering Course at The Evergreen State College

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. ---------------- 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 " ---------------- 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. ------------- Chapter 8 - Class Point..... information hiding encapsulation ------------- Chapter 9 - Other kinds of Browsers class browser hierarchy browser spawn hierarchy Beware of changing classes w/ multiple browsers open! use update! ------------- 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. [ SOS Home Page | Case Study | Year Long Projects | OOP ]