Rails HABTM display and select - sql

Question

I am trying to set up in rails 3.2.0 with ruby 1.9.3 a
has_and_belongs_to_many relationship between two tables I have the proper join table migration set up with both foreign keys and my models are as such
student.rb
class Student < ActiveRecord::Base
attr_accessible :birthday, :id, :name, :year, :course_ids
has_and_belongs_to_many :courses
accepts_nested_attributes_for :courses
end
course.rb
class Course < ActiveRecord::Base
attr_accessible :id, :coursePrefix, :roomNumber, :name, :student_ids
has_and_belongs_to_many :students
end
_form.html.erb
<%= form_for(#student) do |f| %>
<% if #student.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(#student.errors.count, "error") %> prohibited this student from being saved:</h2>
<ul>
<% #student.errors.full_messages.each do |msg| %>
<li><%= msg %></li>
<% end %>
</ul>
</div>
<% end %>
<div class="field">
<%= f.label :id %><br />
<%= f.text_field :id %>
</div>
<div class="field">
<%= f.label :name %><br />
<%= f.text_field :name %>
</div>
<div class="field">
<%= f.label :birthday %><br />
<%= f.date_select :birthday, :start_year => 1930 %>
</div>
<div class="field">
<%= f.label :year %><br />
<%= f.text_field :year %>
</div>
<div>
<%= f.collection_select(:courses, #courses, :id, :name)%>
</div>
<br />
<div class="actions">
<%= f.submit %>
</div>
<% end %>
and student_controller.rb
# GET /students/new
# GET /students/new.json
def new
#student = Student.new
#courses = Course.all
respond_to do |format|
format.html # new.html.erb
format.json { render json: #student }
end
end
# GET /students/1/edit
def edit
#student = Student.find(params[:id])
#courses = Course.all
end
# POST /students
# POST /students.json
def create
#student = Student.new(params[:student])
respond_to do |format|
if #student.save
format.html { redirect_to #student, notice: 'Student was successfully created.' }
format.json { render json: #student, status: :created, location: #student }
else
format.html { render action: "new" }
format.json { render json: #student.errors, status: :unprocessable_entity }
end
end
end
# PUT /students/1
# PUT /students/1.json
def update
#student = Student.find(params[:id])
#courses = #student.courses.find(:all)
respond_to do |format|
if #student.update_attributes(params[:student])
format.html { redirect_to #student, notice: 'Student was successfully updated.' }
format.json { head :no_content }
else
format.html { render action: "edit" }
format.json { render json: #student.errors, status: :unprocessable_entity }
end
end
end
Again I am trying to get the form element to allow a student to select a course and be saved in that table under the JOIN method, however everytime I try to look for help I get different errors and cannot find a solution
Thank you for your help

Answer 1

You just have to give access to the :courses attribute of the Student model:
class Student < ActiveRecord::Base
attr_accessible :birthday, :id, :name, :year, :course_ids, :courses
# ^ ^ ^ ^
Why? Because your controller receive params formatted like this:
params = {
student: {
id: 12,
name: "Bob the Sponge",
courses: [5, 7], # Course ids
etc: ...
}
}
And the controller is trying to create a Student object directly with the params, so when he is trying to update the courses attribute of the Student, it can't because you didn't define it as accessible.