" CS 1621 Fall 2005
   Demonstration of inheritance and polymorphic access in Smalltalk
   Note how easy it is to mix types and access them in a polymorphic
   way. "

| s p flag type value |
People := Dictionary new.

flag := Prompter prompt: 'Read more data? (y/n)'
                 default: ''.
[flag = 'y']
     whileTrue: [
          "Here we are reading in the class name from the user.  We must
           save it as a symbol, then access the Smalltalk dictionary at
           that key to obtain the actual class.  Once we have the class we
           can create a new instance of the class using the default
           constructor."
          type := (Prompter prompt: 'Class type?'
                           default: '') asSymbol.
          type := Smalltalk at: type.
          p := type new.
          p getData.  "Call getData method"
          People at: (p name) put: p.  "Use name as the key"
          p printString printNl.
          flag := Prompter prompt: 'Read more data? (y/n)'
                            default: ''.
     ].

     "Try different fields here for sorting.  In particular, try a field
      that only exists in Student with a collection containing only
      Students, then try it on a collection containing some Persons as
      well"

s := (Prompter prompt: 'Field to sort on?'
                 default: '') asSymbol.
p := SortedCollection sortBlock:
           [:a :b | (a perform: s) < (b perform: s)].
People do: [ :x | p add: x].

p do: [:x | (x printString) printNl.  '' printNl].
!