Template Method Pattern

Objectives

During this activity:

Students will write and test Ruby code that implements the Template Method design pattern.

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

This activity can be developed individually or in pairs.

Create a folder called templatemethod. Inside this folder, create three files called: table_generator.rb, tc_table_generator.rb, and student.rb.

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

# Template Method Pattern
# Date: 5-Sep-2014
# Authors:
#          456654  Thursday Rubinstein 
#          1160611 Anthony Stark

The initial content of the table_generator.rb and student.rb files should be as follows. Study them carefully so you understand how they work.

# File name: table_generator.rb

class TableGenerator

  def initialize(header, data)
    @header = header
    @data = data
  end

  def generate
    generate_header_row + (@data.map {|x| generate_row(x)}).join
  end

  def generate_header_row
    (@header.map {|x| generate_header_item(x)}).join
  end

  def generate_item(item)
    item
  end

  def generate_row(row)
    (row.map {|x| generate_item(x)}).join
  end

  def generate_header_item(item)
    item
  end

end

class CSVTableGenerator < TableGenerator

  def generate_row(row)
    "#{(row.map {|x| generate_item(x)}).join(',')}\n"
  end

  def generate_header_row
    generate_row(@header)
  end

end

# File name: student.rb

class Student

  include Enumerable
  # Note: This class does not support the max, min, or sort methods.

  def initialize(id, name, grades)
    @id = id
    @name = name
    @grades = grades
  end

  def inspect
    "Student(#{@id}, #{@name.inspect})"
  end

  def grade_average
    @grades.inject(:+)/@grades.size
  end

  def each &block
    yield @id
    yield @name
    @grades.each(&block)
    yield grade_average
  end

end

The TableGenerator and its subclass CSVTableGenerator (CSV stands for Comma-separated values) are an implementation of the Template Method pattern. Given some tabular data, they allow generating tables in different kinds of text formats. The Student class will be used when testing.

In the table_generator.rb source file, write the following classes: HTMLTableGenerator and AsciiDocTableGenerator. These classes must extend TableGenerator and override the appropriate methods so that the following unit tests work as expected. Place the test class in the source file called tc_table_generator.rb.

# File name: tc_table_generator.rb

require 'test/unit'
require 'table_generator'
require 'student'

class TableGeneratorTest < Test::Unit::TestCase

  def setup
    @headerEmpty = []
    @dataEmpty = []

    @headerNums = %w{Snap Crackle Pop}
    @dataNums = [[10, 20, 30],
                 [12, 64, 13],
                 [34, 11, 29],
                 [99, 15, 34]]

    @headerStudents = %w{id name grade1 grade2 grade3 average}
    @dataStudents = [Student.new(123, "Selma Bouvier", [71, 84, 89]),
                     Student.new(241, "Carl Carlson", [78, 85, 90]),
                     Student.new(299, "Todd Flanders", [67, 71, 77]),
                     Student.new(311, "Barney Gumble", [24, 18, 35]),
                     Student.new(427, "Edna Krabappel", [92, 95, 99]),
                     Student.new(666, "Damian Thorn", [66, 66, 66]),
                     Student.new(718, "Manjula Nahasapeemapetilon", [53, 72, 88])]
  end

  def test_CSVTableGenerator
    assert_equal \
      "Snap,Crackle,Pop\n" +
      "10,20,30\n" +
      "12,64,13\n" +
      "34,11,29\n" +
      "99,15,34\n",
      CSVTableGenerator.new(@headerNums, @dataNums).generate
    assert_equal \
      "id,name,grade1,grade2,grade3,average\n" +
      "123,Selma Bouvier,71,84,89,81\n" +
      "241,Carl Carlson,78,85,90,84\n" +
      "299,Todd Flanders,67,71,77,71\n" +
      "311,Barney Gumble,24,18,35,25\n" +
      "427,Edna Krabappel,92,95,99,95\n" +
      "666,Damian Thorn,66,66,66,66\n" +
      "718,Manjula Nahasapeemapetilon,53,72,88,71\n",
      CSVTableGenerator.new(@headerStudents, @dataStudents).generate
  end

  def test_HTMLTableGenerator
    assert_equal \
      "<table>\n" +
      "<tr><th>Snap</th><th>Crackle</th><th>Pop</th></tr>\n" +
      "<tr><td>10</td><td>20</td><td>30</td></tr>\n" +
      "<tr><td>12</td><td>64</td><td>13</td></tr>\n" +
      "<tr><td>34</td><td>11</td><td>29</td></tr>\n" +
      "<tr><td>99</td><td>15</td><td>34</td></tr>\n" +
      "</table>\n",
      HTMLTableGenerator.new(@headerNums, @dataNums).generate
    assert_equal \
      "<table>\n" +
      "<tr><th>id</th><th>name</th><th>grade1</th>" +
      "<th>grade2</th><th>grade3</th><th>average</th></tr>\n" +
      "<tr><td>123</td><td>Selma Bouvier</td><td>71</td>" +
      "<td>84</td><td>89</td><td>81</td></tr>\n" +
      "<tr><td>241</td><td>Carl Carlson</td><td>78</td>" +
      "<td>85</td><td>90</td><td>84</td></tr>\n" +
      "<tr><td>299</td><td>Todd Flanders</td><td>67</td>" +
      "<td>71</td><td>77</td><td>71</td></tr>\n" +
      "<tr><td>311</td><td>Barney Gumble</td><td>24</td>" +
      "<td>18</td><td>35</td><td>25</td></tr>\n" +
      "<tr><td>427</td><td>Edna Krabappel</td><td>92</td>" +
      "<td>95</td><td>99</td><td>95</td></tr>\n" +
      "<tr><td>666</td><td>Damian Thorn</td><td>66</td>" +
      "<td>66</td><td>66</td><td>66</td></tr>\n" +
      "<tr><td>718</td><td>Manjula Nahasapeemapetilon</td><td>53</td>" +
      "<td>72</td><td>88</td><td>71</td></tr>\n" +
      "</table>\n",
      HTMLTableGenerator.new(@headerStudents, @dataStudents).generate
  end

  def test_AsciiDocTableGenerator
    assert_equal \
      "[options=\"header\"]\n" +
      "|==========\n" +
      "|Snap|Crackle|Pop\n" +
      "|10|20|30\n" +
      "|12|64|13\n" +
      "|34|11|29\n" +
      "|99|15|34\n" +
      "|==========\n",
      AsciiDocTableGenerator.new(@headerNums, @dataNums).generate
    assert_equal \
      "[options=\"header\"]\n" +
      "|==========\n" +
      "|id|name|grade1|grade2|grade3|average\n" +
      "|123|Selma Bouvier|71|84|89|81\n" +
      "|241|Carl Carlson|78|85|90|84\n" +
      "|299|Todd Flanders|67|71|77|71\n" +
      "|311|Barney Gumble|24|18|35|25\n" +
      "|427|Edna Krabappel|92|95|99|95\n" +
      "|666|Damian Thorn|66|66|66|66\n" +
      "|718|Manjula Nahasapeemapetilon|53|72|88|71\n" +
      "|==========\n",
      AsciiDocTableGenerator.new(@headerStudents, @dataStudents).generate
  end

end

Deliverables

Create a compressed tarball file with the full contents of the templatemethod directory. Call this file templatemethod.tgz. From a terminal, you can use the following command to create this file (make sure to run it at the same level where the templatemethod folder resides):

tar czf templatemethod.tgz templatemethod

✔ Upload Instructions

To deliver the templatemethod.tgz file, please provide the following information:

Request PIN

Due date is Friday, September 5.

S/W Design and Architecture

Template Method Pattern

Objectives

Activity Description

Deliverables

✔ Upload Instructions