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Lab 9: Meta-programming Pattern

Objectives

During this lab session:

This activity helps students develop the following skills, values and attitudes: ability to analyze and synthesize, capacity for identifying and solving problems, and efficient use of computer systems.

Activity Description

IMPORTANT NOTE: The lab activities can be developed individually or in pairs. The lab report must be developed individually.

  1. Create a folder called metaprogramming. Inside this folder, create two files called: attr_init.rb and tc_attr_init.rb.

    All Ruby source files must start with a comment containing the lab’s title, date, and the authors’ personal information. For example:

    # Lab 9: Meta-programming Pattern
    # Date: 10-Apr-2013
    # Authors:
    # 456654  Thursday Rubinstein 
    # 1160611 Anthony Stark
    
  2. In the attr_init.rb source file, open the Object class and define a new class method called attr_init. This method should work as a class annotation that defines the initialize method in the enclosing class, and also calls the attr_accessor as shown as follows.

    For example, given the class definition:

    class C
      attr_init :w, :x, :y, :z
    end
    

    It should be transformed into something equivalent to this:

    class C
      def initialize(w, x, y, z)
        @w = w
        @x = x
        @y = y
        @z = z
      end
      attr_accessor :w, :x, :y, :z
    end
    

    Use the meta-programming pattern, as explained in page 309 of [OLSEN], to do this.

  3. The following unit tests verify the correct definition of the attr_init class annotation. Place the test class in the tc_attr_init.rb source file.

    # File: tc_attr_init.rb
    
    require 'test/unit'
    require 'attr_init'
    
    class AttrInitTest < Test::Unit::TestCase
    
      class Alpha
        attr_init :beta, :gamma, :delta
      end
    
      class BiologicalClassification
        attr_init :kingdom, :phylum, :klass, :order, :family, :genus, :species
      end
    
      def test_alpha
        alpha = Alpha.new('one', 'two', 'three')
        assert_equal 3, alpha.method(:initialize).arity
        assert_respond_to alpha, :beta
        assert_respond_to alpha, :beta=
        assert_respond_to alpha, :gamma
        assert_respond_to alpha, :gamma=
        assert_respond_to alpha, :delta
        assert_respond_to alpha, :delta=
        assert_equal 'one', alpha.beta
        assert_equal 'two', alpha.gamma
        assert_equal 'three', alpha.delta
        assert_equal 1, (alpha.beta = 1)
        assert_equal 2, (alpha.gamma = 2)
        assert_equal 3, (alpha.delta = 3)
        assert_equal 1, alpha.beta
        assert_equal 2, alpha.gamma
        assert_equal 3, alpha.delta
      end
    
      def test_biological_classification
        platapus = BiologicalClassification.new(
          'Animalia',
          'Chordata',
          'Mammalia',
          'Monotremata',
          'Ornithorhynchidae',
          'Ornithorhynchus',
          'Ornithorhynchus Anatinus')
        assert_equal 7, platapus.method(:initialize).arity
        assert_respond_to platapus, :kingdom
        assert_respond_to platapus, :phylum
        assert_respond_to platapus, :klass
        assert_respond_to platapus, :order
        assert_respond_to platapus, :family
        assert_respond_to platapus, :genus
        assert_respond_to platapus, :species
        assert_respond_to platapus, :kingdom=
        assert_respond_to platapus, :phylum=
        assert_respond_to platapus, :klass=
        assert_respond_to platapus, :order=
        assert_respond_to platapus, :family=
        assert_respond_to platapus, :genus=
        assert_respond_to platapus, :species=
        assert_equal 'Animalia', platapus.kingdom
        assert_equal 'Chordata', platapus.phylum
        assert_equal 'Mammalia', platapus.klass
        assert_equal 'Monotremata', platapus.order
        assert_equal 'Ornithorhynchidae', platapus.family
        assert_equal 'Ornithorhynchus', platapus.genus
        assert_equal 'Ornithorhynchus Anatinus', platapus.species
        assert_equal 'Amoebozoa', (platapus.kingdom = 'Amoebozoa')
        assert_equal 'Tubulinea', (platapus.phylum = 'Tubulinea')
        assert_equal 'Tubulinida', (platapus.order = 'Tubulinida')
        assert_equal 'Amoebidae', (platapus.family = 'Amoebidae')
        assert_equal 'Amoeba', (platapus.genus = 'Amoeba')
        assert_equal 'Amoeba Proteus', (platapus.species = 'Amoeba Proteus')
      end
    
      def test_errors
        assert_raise(ArgumentError) do
          alpha = Alpha.new()
        end
        assert_raise(ArgumentError) do
          alpha = Alpha.new(1, 2, 3, 4)
        end
        assert_raise(ArgumentError) do
          alpha = BiologicalClassification.new()
        end
        assert_raise(ArgumentError) do
          alpha = BiologicalClassification.new(
            'Plantae',
            'Magnoliophyta',
            'Magnoliopsida',
            'Rosales',
            'Rosaceae')
        end
      end
    
    end
    

Deliverables

To hand in your individual lab work, follow these instructions.

Due date is Tuesday, April 16.

Evaluation

This activity will be evaluated using the following criteria:

50% Implementation of functional requirements.
50% Lab report.
DA The program and/or report was plagiarized.