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Copy v clone
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):
   • Ruby training - some fresh examples for string handling applications - [link]

Source code: O2.rb Module: R108

# Copy v clone. If you assign an object, you'll not be creating a new one but just
# copying the reference (instance variable). But if you clone it, you descend into the
# content

class Rectangle
        def initialize(w,h)
                @w = w
                @h = h
                @@cc += 1
                @art = (w+3.0) / (h+2.0)
                end

        def getarea()
                @w * @h
                end

        def setwidth(nw)
                @w = nw
                end

        def getcc()
                @@cc
                end

        def to_s()
                "Rectangle, #{@w} by #{@h} in brown"
                end
        @@cc = 0

end

# test harness - only run if stand alone

if __FILE__ == $0

# copy and clone an object. Copying gives a second name to the same object, but
# cloning duplicates the object

        first = Rectangle.new(12,4)
        second = Rectangle.new(13,2.5)
        third = first.clone
        fourth = first

        first.setwidth(20)

        puts first.getarea()
        puts second.getarea()
        puts third.getarea()
        puts fourth.getarea()

        puts "Number created - #{first.getcc}"

        p first
        print first
        puts first

        print "\n\n\n"

        p first.class
        p first.methods
        p first.instance_variables

        end

__END__

92:februb grahamellis$ ruby O2.rb
80
32.5
48
80
Number created - 2
#<Rectangle:0x100153e10 @h=4, @w=20, @art=2.5>
Rectangle, 20 by 4 in brownRectangle, 20 by 4 in brown

Rectangle
["inspect", "tap", "clone", "public_methods", "object_id", "__send__",
"instance_variable_defined?", "equal?", "freeze", "extend", "send",
"methods", "hash", "dup", "to_enum", "instance_variables", "getarea",
"eql?", "instance_eval", "id", "singleton_methods", "taint", "frozen?",
"instance_variable_get", "enum_for", "setwidth", "instance_of?",
"display", "to_a", "method", "type", "instance_exec", "protected_methods",
"==", "===", "instance_variable_set", "kind_of?", "respond_to?", "to_s",
"class", "__id__", "tainted?", "=~", "private_methods", "untaint", "nil?",
"is_a?", "getcc"]
["@h", "@w", "@art"]
92:februb 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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