CSC/ECE 517 Fall 2014/oss E1460 aua: Difference between revisions
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Revision as of 21:01, 28 October 2014
Expertiza - Refactoring StudentQuizController
Expertiza is a web application developed using Ruby on Rails that serves as a peer-review system. The application allows students to submit and peer-review learning objects (articles, code, web sites, etc)<ref>Expertiza on GitHub</ref><ref>Expertiza Wiki Page</ref>. It is an open source project and it's codebase is maintained in GitHub. We are contributing to Expertiza as a part of our Object-Oriented Design and Development's Open-Source Software (OSS) Project. Our goal in this project is to refactor the Student Quiz Controller. In this Wiki Page, we would be explaining the changes that we have made for the same.
Project Description
Our Goal in this project is to refactor the StudentQuiz controller. This class records the quizzes that the student has attempted and its progress and also submits grades for the essays in the quizzes attempted by the student. The changes that are needed to be done are described as follows:<ref>GoogleDoc for our project requirements</ref>
- Pluralize the class (StudentQuizzesController).
- Rename methods to conform to RESTful style (Rename the list method to index.)
- Reduce the number of instance variables per controller action.
- Review Method graded? for boolean zen.
- Performing Code cleanup by removing unused code.
- Using good Ruby style guidelines in the code.
- Splitting a method performing multiple tasks, into seperate methods
- Fixing logical errors in the code
Modification to Existing Code
Pluralized the class name StudentQuizController
As per the Rails convention the controller class names are suggested to be plural. This helps in generating RESTful routing URI helpers. Also, naming the classes as plural seems intuitive.<ref>http://stackoverflow.com/questions/646951/singular-or-plural-controller-and-helper-names-in-rails</ref>. We used the refactor functionality in RubyMine to rename the StudentQuiz controller class to StudentQuizzes.
The following files were modified and/or renamed.
app/controllers/review_mapping_controller.rb app/controllers/{student_quiz_controller.rb → student_quizzes_controller.rb} app/helpers/student_quiz_helper.rb app/helpers/student_quizzes_helper.rb app/views/questionnaires/view.html.erb app/views/{student_quiz → student_quizzes}/_quiz_form.html.erb app/views/{student_quiz → student_quizzes}/_responses.html.erb app/views/{student_quiz → student_quizzes}/_set_dynamic_quiz.html.erb app/views/{student_quiz → student_quizzes}/_set_self_quiz.html.erb app/views/{student_quiz → student_quizzes}/finished_quiz.html.erb app/views/{student_quiz → student_quizzes}/grade_essays.html.erb app/views/{student_quiz → student_quizzes}/list.html.erb app/views/{student_quiz → student_quizzes}/take_quiz.html.erb app/views/student_task/view.html.erb app/views/tree_display/actions/_assignments_actions.html.erb test/functional/{student_quiz_controller_test.rb → student_quizzes_controller_test.rb} test/test_helper.rb test/unit/helpers/student_quiz_helper_test.rb test/unit/helpers/student_quizzes_helper_test.rb
The detailed change-set for this refactor can be seen here.
RESTful style implementation
The purpose of the list method in the StudentQuizzes controller is to list all the quizzes that are available to a particular user for a particular assignment. RESTful guidelines state that a method that returns a list of all available objects, in this case the quizzes, should be named as index. Therefore, we renamed the list method to the index method in the controller and in all the files that had references to the list method of the student_quizzes_controller (For e.g. :- The view finished_quiz.html.erb of the Student Quiz controller, the review_mapping controller.rb etc.).
Before Refactoring :
student_quizzes_controller.rb
def list @participant = AssignmentParticipant.find(params[:id]) return unless current_user_id?(@participant.user_id) @assignment = Assignment.find(@participant.parent_id) # Find the current phase that the assignment is in. @quiz_phase = @assignment.get_current_stage(AssignmentParticipant.find(params[:id]).topic_id) @quiz_mappings = QuizResponseMap.where(reviewer_id: @participant.id) # Calculate the number of quizzes that the user has completed so far. @num_quizzes_total = @quiz_mappings.size @num_quizzes_completed = 0 @quiz_mappings.each do |map| @num_quizzes_completed += 1 if map.response end if @assignment.staggered_deadline? @quiz_mappings.each { |quiz_mapping| if @assignment.team_assignment? participant = AssignmentTeam.get_first_member(quiz_mapping.reviewee_id) else participant = quiz_mapping.reviewee end if !participant.nil? and !participant.topic_id.nil? quiz_due_date = TopicDeadline.where(topic_id: participant.topic_id, deadline_type_id: 1).first end } deadline_type_id = DeadlineType.find_by_name('quiz').id end end }
After Refactoring :
def index participant = AssignmentParticipant.find(params[:id]) return unless current_user_id?(participant.user_id) @assignment = Assignment.find(participant.parent_id) @quiz_mappings = QuizResponseMap.get_mappings_for_reviewer(participant.id) end
Instance Variable Reductions
In Rails, the data is shared between the controllers and views through the instance variables. The instance variabIes that are set during the execution a particular controller method are accessible to the view. Excessive usage of this standard method of data sharing between the controller and the view results in increased coupling between them. <ref>http://blog.remarkablelabs.com/2013/01/how-to-decrease-coupling-in-your-controllers-views-with-decent_exposure-for-better-maintainability</ref> Increased coupling results in several problems, including less maintainability of code, difficulty in code reuse etc. <ref>http://en.wikipedia.org/wiki/Coupling_(computer_programming)#Disadvantages</ref> Thus, we need to reduce coupling as much as possible and in this case it can be achieved by reducing as many instance variables as possible in the controller. Therefore, we have refactored our code in order to eliminate unnecessary instance variables and to convert all the instance variables to local variables that are not used in the views.
student_quizzes_controller.rb
In the take_quiz method, the following instance variables were removed:
- Changed the quizzes instance variable to a local variable.
- Eliminated the instance variable assignment which was not being used anywhere.
- Eliminated the local variable teams which was not being used any where
The unified diff of the changes made is shown below:
Before Refactoring
def self.take_quiz assignment_id , reviewer_id @quizzes = Array.new reviewer = Participant.where(user_id: reviewer_id, parent_id: assignment_id).first @assignment = Assignment.find(assignment_id) teams = TeamsUser.where(user_id: reviewer_id) Team.where(parent_id: assignment_id).each do |quiz_creator| unless TeamsUser.find_by_team_id(quiz_creator.id).user_id == reviewer_id Questionnaire.where(instructor_id: quiz_creator.id).each do |questionnaire| if !@assignment.team_assignment? unless QuizResponseMap.where(reviewed_object_id: questionnaire.id, reviewer_id: reviewer.id).first @quizzes.push(questionnaire) end else unless QuizResponseMap.where(reviewed_object_id: questionnaire.id, reviewer_id: reviewer_id).first @quizzes.push(questionnaire) end end end end end return @quizzes end
After Refactoring
def self.take_quiz assignment_id , reviewer_id quizzes = Array.new reviewer = Participant.where(user_id: reviewer_id, parent_id: assignment_id).first Team.where(parent_id: assignment_id).each do |quiz_creator| unless TeamsUser.find_by_team_id(quiz_creator.id).user_id == reviewer_id Questionnaire.where(instructor_id: quiz_creator.id).each do |questionnaire| unless QuizResponseMap.where(reviewed_object_id: questionnaire.id, reviewer_id: reviewer.id).first quizzes.push(questionnaire) end end end end return quizzes end
Elimination of Boolean Zen
In cases where a method only returns a boolean value by evaluating an expression (using the if..else construct), the if..else statement is redundant and can be eliminated. We have a method graded? that does this thing. Thus, we eliminated the if..else construct in the graded? method as it was redundant.<ref>https://www.cs.utexas.edu/~scottm/cs312/handouts/slides/topic16_boolean_logic.pdf</ref>
Before Refactoring
student_quizzes_controller.rb
def graded?(response, question) if Score.where(question_id: question.id, response_id: response.id).first return true else return false end end
After Refactoring
def graded?(response, question) return (Score.where(question_id: question.id, response_id: response.id).first) end
Code Cleanup
At some places, we found certain statements and variable assignments that were not being used later on in the method or code. We have eliminated such unused statements, so that methods contain only code that is being used later on. This would improve the readability and the maintainability of the code. For example in the code below we eliminated the @quiz_phase and the @num_quizzes_total variables because they were not being used anywhere in the code. Also, since the local variables quiz_due_date, deadline_type_id, participant were not being used anywhere, we could eliminate the entire if block from the code below. We then converted the instance variable participant to a local variable because it was not being used in the corresponding view.
Before Refactoring
student_quizzes_controller.rb
def list @participant = AssignmentParticipant.find(params[:id]) return unless current_user_id?(@participant.user_id) @assignment = Assignment.find(@participant.parent_id) # Find the current phase that the assignment is in. @quiz_phase = @assignment.get_current_stage(AssignmentParticipant.find(params[:id]).topic_id) @quiz_mappings = QuizResponseMap.where(reviewer_id: @participant.id) # Calculate the number of quizzes that the user has completed so far. @num_quizzes_total = @quiz_mappings.size @num_quizzes_completed = 0 @quiz_mappings.each do |map| @num_quizzes_completed += 1 if map.response end if @assignment.staggered_deadline? @quiz_mappings.each { |quiz_mapping| if @assignment.team_assignment? participant = AssignmentTeam.get_first_member(quiz_mapping.reviewee_id) else participant = quiz_mapping.reviewee end if !participant.nil? and !participant.topic_id.nil? quiz_due_date = TopicDeadline.where(topic_id: participant.topic_id, deadline_type_id: 1).first end } deadline_type_id = DeadlineType.find_by_name('quiz').id end end }
After Refactoring
def index participant = AssignmentParticipant.find(params[:id]) return unless current_user_id?(participant.user_id) @assignment = Assignment.find(participant.parent_id) @quiz_mappings = QuizResponseMap.get_mappings_for_reviewer(participant.id) end
Following Ruby Style Guidelines (Global Rules)
At many places in the code we found that the Ruby Style Guidelines were not followed. We have refactored the code so that it uses the good code style guidelines. The following are some of the refactorings the we have done:-
Used .eql? instead of "=="
Before Refactoring
student_quizzes_controller.rb
Method : finished_quiz
if score.score == -1
After Refactoring
if score.score.eql? -1
Eliminated the "== true/false" check
Before Refactoring
student_quizzes_controller.rb
Method : finished_quiz
if essay_not_graded == true
After Refactoring
if essay_not_graded
Use `&&` and `||` rather than `and` and `or` to keep boolean precedence
Before Refactoring
student_quizzes_controller.rb
Method: record_response
elsif correct_answer and params["#{question.id}"] == correct_answer.txt
After Refactoring
student_quizzes_controller.rb
Method: calculate_score
elsif correct_answer && params["#{question.id}"]== correct_answer.txt
Use key: ‘value’, not :key => ‘value’
Before Refactoring
student_quizzes_controller.rb
Method: record_response
new_score = Score.new :comments => choice, :question_id => question.id, :response_id => @response.id
After Refactoring
student_quizzes_controller.rb
Method: calculate_score
new_score = Score.new comments: choice, question_id: question.id, response_id: response.id
Replace find_by_... with a where command
Rails 4 conventions dictate the use of 'where()' over the use of 'find_by_...' methods while querying ActiveRecords. The code has been refactored to replace the usages of find_by.. with where().
Before Refactoring
student_quizzes_controller.rb
Method: record_response
if (QuestionType.find_by_question_id question.id).q_type == 'MCC'
After Refactoring
student_quizzes_controller.rb
Method: calculate_score
ques_type = (QuestionType.where( question_id: question.id)).q_type if ques_type.eql? 'MCC'
Used .nil? instead of "== nil"
The inbuilt method .nil? returns a boolean.
we have used this to replace an == nil check that was there in the code.
Before Refactoring
student_quizzes_controller.rb
Method: record_response
if params["#{question.id}"] == nil
After Refactoring
student_quizzes_controller.rb
Method: calculate_score
if params["#{question.id}"].nil?
Used a Boolean variable when that is sufficient
It is a good practice to use a boolean variable if we only need a boolean for our purpose.
Before Refactoring
student_quizzes_controller.rb
Method: record_response
valid = 1 if valid == 0
After Refactoring
student_quizzes_controller.rb
Method: calculate_score
valid = false if valid
Use good conditional statements
Using unless is a good practice. But it is not a good practice to use unless and ! within the condition.
Instead we could use an if condition itself.
Before Refactoring
student_quizzes_controller.rb
Method: record_response
unless new_score.comments != "" && new_score.comments valid = false
After Refactoring
student_quizzes_controller.rb
Method: calculate_score
if new_score.comments.empty? || new_score.comments.nil? valid = false
Use of Routing Helpers
Routing helpers are a simpler alternative to the otherwise complex hard coded URLs which reduce the readability of the code.Routing helpers allow us to declare possible common routes for a given controller. Routing helpers have been implemented since they maintain consistency even if changes are made to the routing paths.
Before Refactoring:
config.rb does not contain a student_quizzes resource
review_mapping_controller.rb
redirect_to :controller => 'student_quizzes', :action => 'index', :id => params[:participant_id]
After Refactoring
config.rb
resources :student_quizzes, :only => [:index]
review_mapping_controller.rb
redirect_to student_quizzes_path(:id => params[:participant_id])
Replace controller method with a model method
Rails 4 conventions dictate the use of a fat model and skinny controller. It is better to put place the search function in the model rather than placing it in the controller. The search code belonged to the quiz_response_map model, since it queries that particular table in the DB. The code was extracted into the subsequent method displayed below and called from the invitation controller.<ref name = "stackoverflow">StackOverflow</ref>
Before Refactoring
student_quizzes_controller.rb
@quiz_mappings = QuizResponseMap.where(reviewer_id: participant.id)
After Refactoring
@quiz_mappings = QuizResponseMap.get_mappings_for_reviewer(participant.id)
Changes made in method logic
We have made certain changes in the logic of the methods calculate_score and record_response (previously the code of both these methods was only in record_response) primarily to improve the existing logic and eliminate redundant code. These changes are described as follows:
- The score variable was already being set to 0 on the loop entry, therefore it was redundant to reset score to zero again. Thus, we eliminated this line of code inside the if statement.
Before Refactoring
questions.each do |question| score = 0 if (QuestionType.find_by_question_id question.id).q_type == 'MCC' score = 0
After Refactoring
questions.each do |question| score = 0 if ques_type.eql? 'MCC' # Eliminated score = 0 over here
- The variable correct_answer stored multiple values as the where condition to which it was assigned was returning multiple values. Therefore it seemed more intuitive to rename correct_answer to correct_answers so that it is apparent that it contains multiple values.
Before Refactoring
correct_answer = QuizQuestionChoice.where(question_id: question.id, iscorrect: 1)
After Refactoring
correct_answers = QuizQuestionChoice.where(question_id: question.id, iscorrect: true)
- The below piece of code found out the question type twice in the same loop. Therefore we extracted it and assigned it to a local variable so that the query is executed only once.
Before Refactoring
# First Query if (QuestionType.find_by_question_id question.id).q_type == 'MCC' # Repetition of the query in the same loop if (QuestionType.find_by_question_id question.id).q_type == 'Essay'
After Refactoring
# Querying only once and assigning it to a local variable ques_type ques_type = (QuestionType.where( question_id: question.id)).q_type # Usage 1 of ques_type if ques_type.eql? 'MCC' # Usage 2 of ques_type if ques_type.eql? 'Essay'
- The new_scores and scores array stored almost the similar values. The scores contained a copy of the value that the new_scores array contained. Therefore we eliminated the new_scores array and are performing all the operations only on the scores array.
Before Refactoring
# Part 1 new_score = Score.new :comments => choice, :question_id => question.id, :response_id => @response.id unless new_score.valid? valid = 1 end new_scores.push(new_score) # Part 2 new_scores.each do |score_update| score_update.score = score scores.push(score_update) end
After Refactoring
# Part 1 new_score = Score.new comments: choice, question_id: question.id, response_id: response.id unless new_score.valid? valid = false end scores.push(new_score) # Part 2 scores.each do |score_update| score_update.score = score end
- The logic to compute the final score for a multiple-choice, multiple-correct type of question seemed to be incorrect and therefore we fixed it.
Before Refactoring
# Part 1 of the Scoring Logic questions.each do |question| score = 0 if (QuestionType.find_by_question_id question.id).q_type == 'MCC' score = 0 if params["#{question.id}"] == nil valid = 1 else correct_answer = QuizQuestionChoice.where(question_id: question.id, iscorrect: 1) params["#{question.id}"].each do |choice| correct_answer.each do |correct| if choice == correct.txt score += 1 end # Part 2 of the scoring logic which seems to award full points even if you marked some extra options apart from marking all correct answers unless score == correct_answer.count score = 0 else score = 1 end
After Refactoring
# Part 1 of the Scoring Logic questions.each do |question| score = 0 correct_answers = QuizQuestionChoice.where(question_id: question.id, iscorrect: true) ques_type = (QuestionType.where( question_id: question.id)).q_type if ques_type.eql? 'MCC' if params["#{question.id}"].nil? valid = false else params["#{question.id}"].each do |choice| correct_answers.each do |correct| if choice.eql? correct.txt score += 1 end # Part 2 of the scoring logic - We have also compared the number of options the user selected to the total number of correct answers if score.eql? correct_answers.count && score == params["#{question.id}"].count score = 1 else score = 0 end
- The record_response function was performing two distinct operations : One operation was saving the response to the Database and the other was to calculate the score for the questions. We created a new function calculate_score that would calculate the score for the questions and record_response now only performs the task of saving responses to the database.
Before Refactoring
def record_response @map = ResponseMap.find(params[:map_id]) @response = Response.new() @response.map_id = params[:map_id] @response.created_at = DateTime.current @response.updated_at = DateTime.current @response.save @questionnaire = Questionnaire.find(@map.reviewed_object_id) scores = Array.new new_scores = Array.new valid = 0 questions = Question.where(questionnaire_id: @questionnaire.id) questions.each do |question| score = 0 if (QuestionType.find_by_question_id question.id).q_type == 'MCC' score = 0 if params["#{question.id}"] == nil valid = 1 else correct_answer = QuizQuestionChoice.where(question_id: question.id, iscorrect: 1) params["#{question.id}"].each do |choice| correct_answer.each do |correct| if choice == correct.txt score += 1 end end new_score = Score.new :comments => choice, :question_id => question.id, :response_id => @response.id unless new_score.valid? valid = 1 end new_scores.push(new_score) end unless score == correct_answer.count score = 0 else score = 1 end new_scores.each do |score_update| score_update.score = score scores.push(score_update) end end else score = 0 correct_answer = QuizQuestionChoice.where(question_id: question.id, iscorrect: 1).first if (QuestionType.find_by_question_id question.id).q_type == 'Essay' score = -1 elsif correct_answer and params["#{question.id}"] == correct_answer.txt score = 1 end new_score = Score.new :comments => params["#{question.id}"], :question_id => question.id, :response_id => @response.id, :score => score unless new_score.comments != "" && new_score.comments valid = 1 end scores.push(new_score) end end if valid == 0 scores.each do |score| score.save end redirect_to :controller => 'student_quizzes', :action => 'finished_quiz', :map_id => @map.id else flash[:error] = "Please answer every question." redirect_to :action => :take_quiz, :assignment_id => params[:assignment_id], :questionnaire_id => @questionnaire.id end end
After Refactoring
# New record_response method def record_response map = ResponseMap.find(params[:map_id]) response = Response.new response.map_id = params[:map_id] response.created_at = DateTime.current response.updated_at = DateTime.current response.save calculate_score map,response end # New calculate_score def calculate_score map, response # The entire logic below the response.save line from the earlier record_response method goes here.
References
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