undefined method while using form_for in New controller method

Question

Im getting this error on rendering the form for New controller method:

undefined method `teacher_id' for # Extracted source (around line #8):

 <table summary="Student form fields">
  <tr>
    <th>Teacher ID</th>
    <td><%= f.number_field :teacher_id %></td>  # this is line 8
  </tr>
  <tr>
    <th>Parent ID</th>

This is new.html.erb:

<h1>Add A Student</h1>

<%= form_for @student, :url => { :action => 'create'}, :html => { :multipart => true } do |f| %>
<table summary="Student form fields">
   <tr>
     <th>Teacher ID</th>
     <td><%= f.number_field :teacher_id %></td>
   </tr>
   <tr>
     <th>Parent ID</th>
     <td><%= f.number_field :parent_id %></td>
   </tr>
   <tr>
     <th>FirstName</th>
     <td><%= f.text_field :firstname %></td>
   </tr>
   <tr>
     <th>LastName</th>
     <td><%= f.text_field :lastname %></td>
   </tr>
   <tr>
     <th>Date of Birth</th>
     <td><%= f.date_field :dob %></td>
   </tr>
   <tr>
     <th>Email</th>
     <td><%= f.email_field :email %></td>
   </tr>
   <tr>
     <th>Cellphone</th>
     <td><%= f.telephone_field :cellphone %></td>
   </tr>
   <tr>
     <th>Username</th>
     <td><%= f.text_field :username %></td>
   </tr>
   <tr>
   <tr>
     <th>Password</th>
     <td><%= f.password_field :password %></td>
   </tr>
   <tr>
     <th>Confirm Password</th>
     <td><%= f.password_field :password_confirmation %></td>
   </tr>
   <tr>
     <th>Address Street#</th>
     <td><%= f.text_field :addr_streetno %></td>
     <th>Apt #</th>
     <td><%= f.number_field :addr_aptno %></td>
   </tr>
   <tr>
     <th>City</th>
     <td><%= f.text_field :addr_city %></td>
     <th>State</th>
     <td><%= f.text_field :addr_state %></td>
     <th>Zip</th>
     <td><%= f.number_field :addr_zip %></td>
   </tr>
   <tr>
     <th>Photo</th>
     <td><%= f.file_field :photo %></td>
   </tr>
</table>

   <%= f.submit 'Create Student' %>
<% end %>

<% if @student.errors.any? %>
    <ul class="Signup_Errors">
    <% for message_error in @student.errors.full_messages %>
      <li>* <%= message_error %></li>
    <% end %>
    </ul>
  <% end %>
</div>

'This is the student.rb model file:

class Student < ActiveRecord::Base
    #attr_accessor :teacherid, :firstname, :lastname, :dob, :isadult, 
    #              :email, :cellphone, :username, :password, :addr_streetno, 
    #             :addr_city, :addr_state, :addr_zip, :photo

    #has_secure_password

    belongs_to :parent
    belongs_to :teacher

    attr_accessor :email, :password, :password_confirmation

    EMAIL_REGEX = /\A[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\z/i
    validates :username, :presence => true, :uniqueness => true, :length => { :in => 3..20 }
    validates :email, :presence => true, :uniqueness => true, :format => EMAIL_REGEX
    validates_confirmation_of :password

    scope :sorted, lambda { order("students.firstname ASC")}
end

This is the structure of the student table:

create_table :students do |t|
   t.references :parents
   t.references :teachers, null: false

   t.string :firstname, null: false
   t.string :lastname, null: false
   t.date :dob, null: false
   t.boolean :isadult, null: false, default: false
   t.string :email, null: false
   t.string :cellphone
   t.string :username, null: false
   t.string :password_digest, null: false
   t.string :addr_streetno
   t.integer :addr_aptno
   t.string :addr_city
   t.string :addr_state
   t.integer :addr_zip
   t.binary :photo, :limit => 0.5.megabyte

   t.timestamps
 end 

Answer 1

Your table definition says teachers where it should be teacher, since it’s a belongs_to. It should read this way:

t.references :parent
t.references :teacher, null: false

Answer 2

Buck Doyle's answer is right, however, to expand on it, I would mention that when you receive a no method error - it means your object does not have the attributes you're calling

--

Attributes

You have to remember everything in Ruby is an object, which Rails populates with a series of attributes. Although we call them attributes in Rails, the fact is every object (created with a Rails Model / Ruby Class) has a series of methods which are called each time you have an instance of it

Therefore, if you have a model, what you're really doing is defining the attributes / methods which Rails is able to call. That's why you can use virtual attributes with attr_accessor - this tells the model (a Ruby class) to include those methods

Simply, your ActiveRecord objects will always be populated with attributes from your database, as well as any virtual attributes you set. The no method error means you're trying to call attributes which don't exist

--

Fix

The way to fix a no method error is to ensure you have the correct columns in your db

As highlighted by Buck Doyle, the most likely issue you have is you've referenced t.references :teachers, null: false in your migration, which it should be singular