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School3 Example

Directions

1. Create a new Rails project named School3.
2. Generate a Rails scaffold named Student with these fields.

   Field	Datatype
   name	string
   gender	string
   phone	string

3. Generate a Rails scaffold named Course with these fields.

   Field	Datatype
   course_num	string
   title	string
   credit_hours	integer

4. Generate a Rails model (not scaffold) named Enrollment with these fields.

   Field	Datatype
   student_id	integer
   course_id	integer

5. Make these additions to the model files:
   

   # In the School3/app/models/enrollment.rb
   belongs_to :course
   belongs_to :student
   
   # In School3/app/models/course.rb
   has_many :enrollments
   has_many :students, through: :enrollments
   
   # In School3/app/models/student.rb
   has_many :enrollments
   has_many :courses, through: :enrollments
   

6. Source code for the School3 seed file School3/db/seeds.rb.
7. At the bottom of the Course and Student index views, add a link to the index view of the other model.
8. View the show pages with these URLs:
   

   http://localhost:3000/students
   http://localhost:3000/courses
   

9. Modify the Student show view to show the courses in which the student is enrolled:

   <h3>Courses for <%= @student.name %></h3>
   
   <table>
     <tr>
       <th>Course Number</th>
       <th>Course Title</th>
       <th>Credit Hours</th>
     </tr>
   
     <% @student.courses.each do |c| %>
     <tr>
       <td><%= c.course_num %></td>
       <td><%= c.title %></td>
       <td><%= c.credit_hours %></td>
     </tr>
     <% end %>
   </table>
   

10. Modify the Course show view to show the students that are enrolled in the course:
    

    <h3>Students in <%= @course.course_num %></h3>
    
    <table>
      <tr>
        <th>Name</th>
        <th>Gender</th>
        <th>Phone Number</th>
      </tr>
    
      <% @course.students.each do |s| %>
      <tr>
        <td><%= s.name %></td>
        <td><%= s.gender %></td>
        <td><%= s.phone %></td>
      </tr>
      <% end %>
    </table>
    

11. Add a column to the Course index view to show the enrollment number in each course:
    

     <td><%= course.students.count %></td>
    

We now add the capability of enrolling students in new courses.

1. Add these methods to the Student model: enrolled_in?, unenrolled_courses
   

   # Check if student is enrolled in a course
   def enrolled_in?(course)
     return self.courses.include?(course) 
   end
   
   # Get list of all courses that a 
   # student is not enrolled
   def unenrolled_courses
     return Course.all - self.courses
   end

2. Add this method to the Student controller: add_course:
   

   def add_course
     @student = Student.find(params[:id])
     @course = Course.find(params[:course])
   
     if not @student.enrolled_in?(@course)
       enroll = Enrollment.new
       enroll.student_id = @student.id
       enroll.course_id = @course.id
       enroll.save
     end
     redirect_to @student
   end
   

   Add this form to the bottom of the Student show method before the Edit and Back links.
   

   <% if @student.enrollments.count < Course.count %>
     <p>Enroll in a course.</p>
     <%= form_tag add_course_student_path(@student) do %>
       <%= select_tag(:course,
           options_from_collection_for_select(
             @student.unenrolled_courses, :id, :course_num)) %>
       <%= submit_tag 'Enroll' %>
     <% end %>
   <% end %>
   

 resources :students do
  member do
    post :add_course
  end
end