Rails undefined method

Question

I've been trying to get my first Rails code to work for a while now and I still can't seem to get it to work. My latest problem is that I keep getting the following error

'NoMethodError in MessageController#create".

I see that I am trying to pass nil for some variables as shown in the next line

"undefined method `message' for #<Message mess: nil, user: nil>"

However my parameters are passed correctly as I can see in the bottom of the error screen. My code is below. Any help is appreciated.

Controller

class MessageController < ApplicationController
  def new
    @message = Message.new
  end

  def create
    @message = Message.new(user_params)
    @message.mess=params[:mess]
    @message.user=params[:user]
    if @message.save
        redirect_to "http://itworks.com"
    else
        redirect_to "http://myspace.com"
    end
  end

private
  def user_params
    params.require(:message).permit(:mess, :user)
  end
end

View

<%= form_for @message, url: {action: "create"}, html: {class: "nifty_form"} do |f| %>

    <%= f.text_field :mess %><br />

    <%= f.text_field :user %><br />
    <%= f.submit "Create" %>
<% end %>

Answer 1

Strong Parameters

Firstly, you need to read up on Strong Parameters

With Rails 4, to prevent mass assignment, you need to create new ActiveRecord objects using a private method to assign the parameter values you need:

#app/controllers/messages_controller.rb
Class MessagesController < ApplicationController
   def create
      @message = Message.new(message_params)
      @message.save
   end

   private

   def message_params #-> you can call this method what you like :)
       params.require(:message).permit(:mess, :user)
   end
end

This will set the params for your ActiveRecord object from this params hash:

params {
    "message" => { 
        "mess" => "value",
        "user" => "value"
    }
}

This should be passed by your form as it stands; however, if you started to use something like form_tag, you'll end up without the message param, thus preventing the strong params method from working correctly.

--

Form

Your form can be simplified:

<%= form_for @message, html: {class: "nifty_form"} do |f| %>

If you populate the form_for with an ActiveRecord object, Rails should extract the path automatically for you; not that it matters for your error, as your form is sending the request to the create action anyway

--

Method

The no method error is derived from calling a method on an object which either doesn't exist, or does not support the method (unsurprisingly).

In respect to debugging this issue, you basically need to look for where you may be calling .message on the object. This is typically in a view or something (if not in the controller)

With the only reference to .message being in the strong params method you have, I would recommend trying this:

 def create
    @message = Message.new(user_params)
    if @message.save
        redirect_to "http://itworks.com"
    else
        redirect_to "http://myspace.com"
 end

This will make the action conventional, which should give it the best chance of working.

--

Association

The other problem you may have is the ActiveRecord association in your Message model. ActiveRecord associations are defined in the model to give your objects the ability to append associative data

The error you have could come from something like this:

#app/models/message.rb
Class Message < ActiveRecord::Base
    belongs_to :message #-> won't work
end

Answer 2

You have a couple of naming problems:

class MessagesController < ApplicationController
  #Primarily, you want MessagesController, not MessageController. Plural. 

  def new
    @message = Message.new
  end

  def create
    #you should call 'message_params' not 'user_params' as a 
    #parameter in your call to Message.new
    @message = Message.new(message_params)

 # these two lines need to be commented out, as they overwrite the attributes
 # in @message with nil
 #  @message.mess=params[:mess]
 #  @message.user=params[:user]

    if @message.save
      redirect_to "http://itworks.com"
    else
      redirect_to "http://myspace.com"
    end
  end

  private
  #again, message_params, because these are the params that are permitted via
  #a form to the message controller (and therefore model), though this wasn't 
  #technically a problem. You can name your methods anything you want in Ruby.
  #this name is just clearer. 
  def message_params
    params.require(:message).permit(:mess, :user)
  end
end

You can remove the :url => {:action => 'create'} on your call to form_for, as a new record will always get routed to create by f.submit. This allows you to use the same form for editing and creating.