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Inheritance, factories, statics, DATA, lazy ops, to_s
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):
   • Behaviour and test driven development in Ruby using RSpec - [link]

Source code: in4.rb Module: R108

# Inheritance, factories, DATA, lazy ops, to_s - build up example
# Also used (tested) in rspec demo

class Transport
        def getWhere()
                return @dest
        end
        def getNumber()
                return "This is #{@len} vehicles out of #{@@count}"
        end
        def self.create(raw)
                raw = raw.chomp.split "\t"
                item = nil
                if raw[2] == "T" then
                        item = Train.new raw[3].to_i,raw[4].to_i,raw[0],raw[1]
                elsif raw[2] == "B" then
                        item = Bus.new raw[3].to_i,raw[0],raw[1]
                end
                return item
        end
        def self.factory(source=nil)
                if source
                        fh = File.new(source)
                else
                        fh = DATA
                end
                avail = []
                loop do
                        raw = fh.gets
                        if raw.nil? then break end
                        adding = create raw
                        # avail.push adding unless adding.nil?
                        adding.nil? or avail.push adding
                end
                return avail
        end
        def takesMoreThan?(than)
                return getCapacity > than.getCapacity
        end
        def +(that)
                return "yer what?"
        end
        def to_s()
                return "This is a #{self.class} taking #{self.getCapacity}"
        end
        @@count = 0
        def getLength()
                @len * 23
        end
end
class Train < Transport
        def initialize(len,spc,time,dest)
                @len = len
                @spc = spc
                @time = time
                @dest = dest
                @@count += len
        end
        def getCapacity(overload = 1.4)
                if @capa.nil?
                        @capa = (overload * @len * @spc).to_i
                        # puts "working it out"
                else
                        # puts "know that one"
                end
                return @capa
        end
end
class Bus < Transport
        def initialize(spc,time,dest)
                @len = 1
                @spc = spc
                @time = time
                @dest = dest
                @@count += 1
        end
        def getCapacity(overload = 6)
                return (overload + @spc * @len)
        end
        def getLength()
                @len * 14
        end
end
class BendyBus < Bus
        def initialize(spc,time,dest)
                @len = 2
                @spc = spc
                @time = time
                @dest = dest
                @@count += 2
        end
end
# -------------------------------------
if __FILE__ == $0
        # options = Transport.factory("services.txt")
        options = Transport.factory
        options.each do |option|
                begin
                        puts "#{option.getWhere} for #{option.getCapacity} people"
                        puts option.getNumber
                rescue
                        puts "Plonker"
                end
        end

        if options[1].takesMoreThan? options[2]
                puts options[1]
        else
                puts options[2]
        end

end
__END__
06:38 Soton T 3 78
07:18 Bath B 80
07:14 Devizes H 8
07:19 Swindon T 2 79
08:49 Swindon T 1 77
08:19 Swindon T 2 79
09:49 Swindon T 1 77
09:19 Swindon T 2 79
07:49 Swindon T 1 77

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.
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