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Inheritance, Class methods, Attribute Accessors, operator overloading
More Classes and Objects example from a Well House Consultants training course
More on More Classes and Objects [link]
Source code: reallyshort Module: R108

# Inheritance, Class methods, Attribute Accessors, operator overloading
# A really short demonstration in Ruby showing many second level facilities

class Transport
# Please don't use very many class variables!
        @@counter = 0
        attr_accessor :mins

# Dymanic (object) methods can work on @ and @@ variables ...

        def initialize(where,howmany,mins)
                @where = where
                @howmany = howmany
                @mins = mins
                @@counter += 1
        def getdest
        def getpass

# Static (class) methods can ONLY work on @@ variables ...

# define "getcounter" as a static (aka class) method - i.e. one
# that works on the class as a whole and not on individual members
        def Transport.getcounter
class Train < Transport
        def to_s
                "Train to #{@where}"
        def + (second)
                Train.new(self.getdest + " & " + second.getdest,
                        self.getpass + second.getpass,
                        self.mins + second.mins)
class Bus < Transport
        def getpass
                @howmany - 1
        def to_s
                "Slow old Bus to #{@where}"
# ----------------------------------------------------

# I can call a static method even before I "instantise" any
# members of the class.

puts "Total transports - #{Transport.getcounter} "

options = [ Train.new("Swindon",150,25),
        Bus.new("Bath",82,37) ]
for option in options
        destiny = option.getdest
        passengers = option.getpass
        puts "\n#{option}"
        puts "Going to #{destiny} we can carry #{passengers} customers"

# Coupling up two trains ...

joint = options[0] + options[1]
puts joint
destiny = joint.getdest
passengers = joint.getpass
puts "Going to #{destiny} we can carry #{passengers} customers"

puts "Total transports - #{Transport.getcounter} "


munchkin:rs grahamellis$ ruby reallyshort
Total transports - 0

Train to Swindon
Going to Swindon we can carry 150 customers

Train to Southampton
Going to Southampton we can carry 75 customers

Slow old Bus to Trowbridge
Going to Trowbridge we can carry 61 customers

Slow old Bus to Bath
Going to Bath we can carry 81 customers
Train to Swindon & Southampton
Going to Swindon & Southampton we can carry 225 customers
Total transports - 5
munchkin:rs grahamellis$

Learn about this subject
This module and example are covered on the following public courses:
 * Learning to program in Ruby
 * Ruby Programming
Also available on on site courses for larger groups

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