" CS 1621 Fall 2005
  Example of a subclass in Smalltalk. 
"

Person subclass: #Student
  instanceVariableNames: 
    'major gpa'
  classVariableNames: ''
  poolDictionaries: '' !

!Student class methods ! !


!Student methods !

" Here we first call the superclass version of the method
  to utilize its reading functionality, then we read the
  last two fields in here.  Note that because subclasses have
  direct access to superclass instance variables in Smalltalk,
  we could have read them in directly here, but why do that
  when it is already done by the superclass?"
getData
| s |
super getData.
s := Prompter prompt: 'Major? '
     default: ''.
major := s.
s := Prompter prompt: 'GPA? '
     default: ''.
gpa := (s asNumber) asFloat.
^self!

major
"return major of receiver student"
^major!

gpa
"return gpa of receiver student"
^gpa!

" First call super version os printString then append the rest
  to the end of it"
printString
| w |
w := WriteStream on: String new.
w nextPutAll: (super printString) ; nl;
  nextPutAll: 'Major: ' ; nextPutAll: major ; nl ;
  nextPutAll: 'GPA: '.
  gpa printOn: w.
  w nl.
^(w contents)! !