Adapter Pattern

Activity Description

This activity can be developed individually or in pairs.

1. Create a directory called adapter and a subdirectory src within it. Inside the src folder create three files called: simple_queue.rb, queue_adapter.rb, and adapter_test.rb.

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

   # Adapter Pattern
   # Date: 11-Mar-2019
   # Authors:
   #          A00456654 Thursday Rubinstein 
   #          A01160611 Anthony Stark
   

2. The content of the file simple_queue.rb is as follows:

   # File: simple_queue.rb
   
   # IMPORTANT: Do not modify the following class in any way!
   
   class SimpleQueue
   
     def initialize
       @info =[]
     end
   
     def insert(x)
       @info.push(x)
       self
     end
   
     def remove
       if empty?
         raise "Can't remove if queue is empty"
       else
         @info.shift
       end
     end
   
     def empty?
       @info.empty?
     end
   
     def size
       @info.size
     end
   
     def inspect
       @info.inspect
     end
   
   end
   

   The SimpleQueue class contains a First-In First-Out (FIFO) data structure that implements the following methods:

   Method Signature	Description
   insert(x)	Inserts x at the back of this queue. Returns this queue.
   remove	Removes and returns the element at the front of this queue. Raises an exception if this queue happens to be empty.
   empty?	Returns true if this queue is empty, otherwise returns false.
   size	Returns the number of elements currently stored in this queue.

   Write an adapter class called QueueAdapter (place it in the file called queue_adapter.rb) that makes a SimpleQueue instance (as implemented above) behave like a Last-In First-Out (LIFO) stack with the following interface:

   Method Signature	Description
   initialize(q)	Initializes a new stack, using q as the adaptee.
   push(x)	Inserts x at the top of this stack. Returns this stack.
   pop	Returns nil if this stack is empty, otherwise removes and returns its top element.
   peek	Returns nil if this stack is empty, otherwise returns its top element without removing it.
   empty?	Returns true if this stack is empty, otherwise returns false.
   size	Returns the number of elements currently stored in this stack.

   
   
3. The following unit test verifies the correct behavior of the QueueAdapter class. Place the test class in the adapter_test.rb source file.

   # File: adapter_test.rb 
   
   require 'minitest/autorun'
   require 'simple_queue'
   require 'queue_adapter'
   
   class QueueAdapterTest < Minitest::Test
   
     def test_queue_adapter
       q = SimpleQueue.new
       qa = QueueAdapter.new(q)
       assert q.empty?
       assert qa.empty?
       assert_nil qa.pop
       assert_same qa, qa.push("Foo")
       assert_equal "Foo", qa.peek
       refute q.empty?
       refute qa.empty?
       assert_same qa, qa.push("Bar")
       assert_equal "Bar", qa.peek
       assert_same qa, qa.push("Baz").push("Quux")
       assert_equal 4, q.size
       assert_equal 4, qa.size
       assert_equal "Quux", qa.peek
       assert_equal "Quux", qa.pop
       assert_equal "Baz", qa.peek
       assert_equal "Baz", qa.pop
       assert_equal "Bar", qa.peek
       assert_equal "Bar", qa.pop
       assert_equal "Foo", qa.peek
       assert_same qa, qa.push("Goo")
       assert_equal "Goo", qa.peek
       assert_equal "Goo", qa.pop
       assert_equal "Foo", qa.peek
       assert_equal 1, qa.size
       assert_equal "Foo", qa.pop
       assert_nil qa.peek
       assert_nil qa.pop
       assert q.empty?
       assert qa.empty?
       assert_equal 0, q.size
       assert_equal 0, qa.size
     end
   
   end
   

4. Write and generate your program’s documentation as described in: Documenting Ruby Programs.

Deliverables

Create a compressed tarball file with the full contents of the adapter directory (including the generated HTML documentation in the doc subdirectory). Call this file adapter.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 adapter folder resides):

tar czf adapter.tgz adapter

Only one team member needs to upload the file.

Due date is Monday, March 11.

Evaluation

This activity will be evaluated using the following criteria:

50%	Implementation of program requirements.
50%	Documentation.
1	The program and/or documentation was plagiarized.