gistfile1.rb

  # Before
  def show
        
    if current_user.is_admin?
      if params[:assignment].nil?
        @assignments = Assignment.all        
      else
        @assignments = Assignment.where(:student_id => params[:assignment][:id] )    
      end
    else
      @assignments = Assignment.where(:student_id => current_user.id )     
    end
     
  end
  
  # After
  
  def show
    @assignments = current_user.viewable_assignments
    if params[:assignment]
      @assignments = @assignments.where(student_id: paramsp:assignment][:id])
    end
  end

  # In model
  
  def viewable_assignments
    is_admin? ? Assignment.all : assignments
  end