param is missing or the value is empty error while rendering edit form in Rails4.x

Question

Gurus,

I am making a simple edit form and am getting this error in Rails 4.x. The interesting thing is that the edit.html.erb is basically a copy of new.html.erb for the most part and the new.html.erb is working just fine.

The error is:

param is missing or the value is empty: teacher

def teacher_params
  params.require(:teacher).permit(:firstname, 
                                  :lastname,  
                                  :email, 
                                  :cellphone, 

The application trace is:

app/controllers/teacher_controller.rb:39:in `teacher_params'
app/controllers/teacher_controller.rb:23:in `edit'

The edit form is:

<h1>Add A teacher</h1>

<%= form_for @teacher, :url => { :action => 'edit'}, :id => @teacher.id, :html => { :multipart => true } do |f| %>
<table summary="teacher form fields">
   <tr>
     <th>First Name*</th>
     <td><%= f.text_field :firstname %></td>
   </tr>
   <tr>
     <th>Last Name*</th>
     <td><%= f.text_field :lastname %></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 'Update teacher' %>
<% end %>

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

The model is:

class Teacher < ActiveRecord::Base

has_many :students

has_secure_password

EMAIL_REGEX = /\A[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\z/i
CELLPHONE_REGEX = /\A([0-9]( |-)?)?(\(?[0-9]{3}\)?|[0-9]{3})( |-)?([0-9]{3}( |-)?[0-9]{4}|[a-zA-Z0-9]{7})\z/i
validates :firstname, :presence => true
validates :lastname, :presence => true   
validates :username, :presence => true, :uniqueness => true, :length => { :in => 3..20 }
validates :email, :presence => true, :uniqueness => true, :format => EMAIL_REGEX
validates :cellphone, :presence => true, :format => CELLPHONE_REGEX
validates :addr_aptno, numericality: { only_integer: true, :greater_than => 0 }
validates :addr_zip, numericality: { only_integer: true, :greater_than => 0  }
end

Here is the teacher controller:

class TeacherController < ApplicationController def index @teachers= Teacher.all end

  def new
      @teacher = Teacher.new
  end

  def create
      @teacher = Teacher.new(teacher_params)
      if @teacher.save
        flash[:notice] = "Teacher created."
        redirect_to :action => 'index'
      else
        render :action => 'new'
      end
  end

  def edit
     @teacher = Teacher.find(params[:id])
     # Update the object
     if @teacher.update_attributes(teacher_params)
       # If update succeeds, redirect to the list action
       flash[:notice] = "Teacher updated."
       redirect_to :action => 'index'
     else
       # If save fails, redisplay the form so user can fix problems
       render :action => 'edit'
     end
  end

  def show
  end

private

    def teacher_params
      params.require(:teacher).permit(:firstname, 
                                      :lastname,  
                                      :email, 
                                      :cellphone, 
                                      :username, 
                                      :password,
                                      :password_confirmation,
                                      :addr_streetno, 
                                      :addr_aptno, 
                                      :addr_city, 
                                      :addr_state,
                                      :addr_zip, 
                                      :photo)
    end
end

Here is the migration file:

   create_table :teachers do |t|

   t.string :firstname, null: false
   t.string :lastname, null: 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

Essentially, I had to split the edit action in the controller into udpate and edit. I saw a working example on lynda.com and followed it. Also other people said the same thing. Now its working.

I had to add the :patch keywords in routes.rb

match ':controller(/:action/(:id))', :via => [:get, :post, :patch]

The edit form was a replica of the new form except that the action was update instead of create and that the id had to be passed.

<%= form_for @teacher, :url => { :action => 'update', :id => @teacher.id}, :html => { :multipart => true } do |f| %>

This was the new code in the controller:

      def edit
    @teacher = Teacher.find(params[:id])
  end

  def update
     @teacher = Teacher.find(params[:id])
     # Update the object
     if @teacher.update_attributes(teacher_params)
       # If update succeeds, redirect to the list action
       flash[:notice] = "Teacher updated."
       redirect_to :action => 'show', :id => @teacher.id
     else
       # If update fails, redisplay the form so user can fix problems
       render :action => 'edit'
     end
  end

Answer 2

You have to split the edit action into 2 actions since edit is default just a get request:

def edit
  @teacher = Teacher.find(params[:id])
  respond_to { |format| format.html }
end

def update
   @teacher = Teacher.find(params[:id])
   if @teacher.update_attributes(teacher_params)
   ...
end

Also remove :url => { :action => 'edit'} from your form, since it's routing to the update action. This happens automatically if you use <%= form_for @teacher do |f|%>