Abstract Data Type in Ruby

• Access qualifiers:
  • public, protected, private
  • public is default
• Syntax:
  • Class statement is a clause heralding a section, not a syntactic encapsulation
  • Instance variables begin with @
  • Class variables begin with @@
  • Instance methods start with def, end with end
  • Class methods must be qualified with Class name
  • Constructors: called initialize

      class Stack
        # Constructor
        def initialize
          @data = Array.new
          @maxLength = 100
          @topOfStack = -1
        end
      
        # top method
        def top
          @data[@topOfStack]
        end
    
        # Test code
        myStack = Stack.new
        # #{variable} converts value of variable into string
        puts "Top of stack is: #{myStack.top}"
      end
      

• Members:
  • Can be added at any time with an additional class definition
  • Methods can be removed at any time with remove_method
• Client:
  • Everything is an object