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Class demo - lots of extras
More Classes and Objects example from a Well House Consultants training course
More on More Classes and Objects [link]
Source code: multifood.rb Module: R108
=begin 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 namespace. 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. =end module Humphrey class Food attr_reader :itisa def initialize(what,weight,cals) @itisa = what @weight = weight @calories = cals end def getcalories() val = @calories * @weight / 100.0 return "%7.2f" % val end def < (second) return self.getcalories < second.getcalories end def lessthan (second) return (self.getcalories < second.getcalories ? self : second) end def self.least (these) so_far = these[0] (1...(these.length)).each do |tryme| so_far = these[tryme] if these[tryme] < so_far end return so_far end end class Eat < Food attr_reader :dressed @@yums = 0 def initialize(what,weight,cals,dressed = "no") @dressed = dressed super(what,weight,cals) @@yums += 1 end end class Drink < Food def itisa v = super() return "glass of #{v}" end def dressed return "No way" end def to_s return "DRINKIE!" end end end # 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] lunch.push(Humphrey::Drink.new("water",1000,0.5)) lunch.push(Humphrey::Drink.new("Brandy",25,100)) def om.itisa return "disGUSTing" end lunch.each do |current| cals = current.getcalories wot = current.itisa puts "This #{wot} has #{cals} calories" puts "#{current.dressed}" end if pear < bacon puts "#{bacon.itisa}" else puts "#{pear.itisa}" end better = pear.lessthan(bacon) puts "#{better.itisa}" best = Humphrey::Food::least(lunch) puts "#{best.itisa}" puts om p om __END__ Dorothy-2:d3 grahamellis$ ruby multifood.rb This Bacon Sarnie has 150.00 calories yes This Comice Pear has 18.80 calories no 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 DRINKIE! #<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
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