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More Classes and Objects example from a Well House Consultants training course
More on More Classes and Objects [link]

This example is described in the following article(s):
   • Object Oriented Ruby - new examples - [link]

Source code: multifood.rb Module: R108

This example show definition of a number of classes within the
same module ( a module is rather like a class, but you don't
construct object in it ) and the extra layer means you have another
. or :: in the naming, and you create in effect a separate namespace.
This is exactly what you'll want to do if you're sharing a whole set
of classes between applications, to avoid cluttering the application

You'll also find in this example methods for comparing two objects
and for comparing a whole array of objects. The comparator for two
object will be an object method, and will return EITHER true/false or
one of the two objects. The comparator for the whole array of objects
will be a static (or class) method, and will return an object.

This example also shows inheritance (and how you call the base class
method of the same name as the method you're in with super). It shows
how attributes are overridden as necessary by methods - how the whole
lot work well together.

There's also an example of a singleton method - a method that's unique
to one specific object - which is defined in the test code. Such a
method can't actually be created until after the creation of the object.

module Humphrey
class Food
attr_reader :itisa
def initialize(what,weight,cals)
        @itisa = what
        @weight = weight
        @calories = cals
def getcalories()
        val = @calories * @weight /
        return "%7.2f" % val
def < (second)
        return self.getcalories < second.getcalories
def lessthan (second)
        return (self.getcalories < second.getcalories ? self : second)
def self.least (these)
        so_far = these[0]
        (1...(these.length)).each do |tryme|
                so_far = these[tryme] if these[tryme] < so_far
        return so_far

class Eat < Food
attr_reader :dressed
@@yums = 0
def initialize(what,weight,cals,dressed = "no")
        @dressed = dressed
        @@yums += 1
class Drink < Food
        def itisa
                v = super()
                return "glass of #{v}"
        def dressed
                return "No way"
        def to_s
                return "DRINKIE!"

# Here is our test code
bacon = Humphrey::Eat.new("Bacon Sarnie",75,200,"yes")
pear = Humphrey::Eat.new("Comice Pear",47,40,"no")
om = Humphrey::Drink.new("Orange Milk",250,70)
lunch = [bacon, pear, om]

def om.itisa
        return "disGUSTing"

lunch.each do |current|
        cals = current.getcalories
        wot = current.itisa
        puts "This #{wot} has #{cals} calories"
        puts "#{current.dressed}"

if pear < bacon
        puts "#{bacon.itisa}"
        puts "#{pear.itisa}"

better = pear.lessthan(bacon)
puts "#{better.itisa}"

best = Humphrey::Food::least(lunch)
puts "#{best.itisa}"

puts om
p om


Dorothy-2:d3 grahamellis$ ruby multifood.rb
This Bacon Sarnie has 150.00 calories
This Comice Pear has 18.80 calories
This disGUSTing has 175.00 calories
No way
This glass of water has 5.00 calories
No way
This glass of Brandy has 25.00 calories
No way
Bacon Sarnie
Comice Pear
glass of water
#<Humphrey::Drink:0x25404 @calories=70, @weight=250, @itisa="Orange Milk">
Dorothy-2:d3 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

Books covering this topic
Yes. We have over 700 books in our library. Books covering Ruby are listed here and when you've selected a relevant book we'll link you on to Amazon to order.

Other Examples
This example comes from our "More Classes and Objects" training module. You'll find a description of the topic and some other closely related examples on the "More Classes and Objects" module index page.

Full description of the source code
You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License.

Other resources
• Our Solutions centre provides a number of longer technical articles.
• Our Opentalk forum archive provides a question and answer centre.
The Horse's mouth provides a daily tip or thought.
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• All of these resources can be searched through through our search engine
• And there's a global index here.

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