Question

I’m getting this error when I try to submit my form (/POSTS/SHOW):

RuntimeError in Posts#show

Showing /Users/fkhalid2008/loand/app/views/posts/show.html.erb where line #1 raised:

Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id
Extracted source (around line #1):

1: <%= form_remote_tag (:update => 'message', :url => {:controller => 'main', :action => 'send_message', :user_id => @post.user.id}) do %>
2: <br>
3: <br />
4: <br />

How do I fix this?

Relevant code is below:

/VIEWS/POSTS/SHOW

<%= form_remote_tag (:update => 'message', :url => {:controller => 'main', :action => 'send_message', :user_id => @post.user.id}) do %>
<br>
<br />
<br />
<div class="field">

Hello! My name is <%= f.text_field :subject %> and I’m contacting you in response to your ad. I’m interested in learning more so get in touch! Here’s my contact details: <%= f.text_field :body %>.

Submit
<% end %>

POST MODEL

class Post < ActiveRecord::Base

belongs_to :user

attr_accessible :title, :job, :location, :salary

validates :title, :job, :location, :salary, :presence => true 
validates :salary, :numericality => {:greater_than_or_equal_to => 1} 

default_scope :order => 'posts.created_at DESC'
end

USER MODEL

class User < ActiveRecord::Base

has_many :posts  
has_one :profile
has_private_messages

attr_accessible :email

validates_presence_of :email
validates_uniqueness_of :email, :message =>"Hmm, that email's already taken"
validates_format_of :email, :with => /^([^\s]+)((?:[-a-z0-9]\.)[a-z]{2,})$/i, :message => "Hi! Please use a valid email"


end

POSTS CONTROLLER

def show
@post = Post.find(params[:id]) 

respond_to do |format|
  format.html # show.html.erb
  format.json { render :json => @post }
end
end

def new
@post = Post.new
@post.user = current_user

respond_to do |format|
  format.html # new.html.erb
  format.json { render :json => @post }
end
end

def edit
@post = Post.find(params[:id])
end

def create
    @post = Post.new(params[:post])
    @post.user = current_user

    respond_to do |format|
        if verify_recaptcha && @post.save
            format.html { redirect_to :action=> "index"}
            format.json { render :json => @post, :status => :created, :location => @post }
        else
            format.html { render :action => "new" }
            format.json { render :json => @post.errors, :status => :unprocessable_entity }
        end
    end
end

def update
@post = Post.find(params[:id])
@post.user = current_user

respond_to do |format|
  if @post.update_attributes(params[:post])
    format.html { redirect_to @post, :notice => 'Post was successfully updated.' }
    format.json { head :ok }
  else
    format.html { render :action => "edit" }
    format.json { render :json => @post.errors, :status => :unprocessable_entity }
  end
end
end 

APPLICATION CONTROLLER (this is where I am defining current_user)

class ApplicationController < ActionController::Base
protect_from_forgery

private

def current_user
    @_current_user ||= session[:current_user_id] &&
    User.find_by_id(session[:current_user_id])
end

end

MAIN CONTROLLER (send_message is defined here)

class MainController < ApplicationController

def send_message
message = Message.new
message.subject = params[:subject]
message.body = params[:message]
message.sender = User.find session[:user]
message.recipient = User.find params[:user_id]
if message.save
  ContactMailer.deliver_message_email message.recipient.email, message.id, request.host
  return redirect_to "/posts"
else
  render :text => "Hmm. Something seems to be wrong...let me look into it"
end
end

Answer 1

You don’t have a user assigned to the post record represented by the @post instance variable.

Presumably a user needs to be logged in to make a post?
Also presumably you have a current user defined somewhere?

Your controller actions that use this form need to assign the user to the post record

def new
  @post = Post.new
  @post.user = current_user # You will need to get the current user from somewhere
  respond_to do |format|
    format.html # new.html.erb
    format.json { render :json => @post }
  end
end

UPDATE

To make sure that your current user is assigned you should add a check to ensure the user is logged in in the controller actions. This is normally done by adding a before filter to authorize the current user which will redirect back to the login page if the current use is logged out.
Have a look at this rails cast to explain logging in and out and redirecting on a before filter http://railscasts.com/episodes/250-authentication-from-scratch

There is a revised version of the cast here but you will need a subscription for that
http://railscasts.com/episodes/250-authentication-from-scratch-revised

well worth paying for IMO

End of update

You will need to / should also assign the current user in whatever actions update the post record – i.e. the create and update actions in EXACTLY the same way.

Also, because you have not got a user assigned to a post record then you need to handle this scenario in the form so that you don’t get 500 errors

You can use the @post.user.blank? boolean check to help you with this
Something like

<% if @post.user.blank? %>
  <h2>There is no user assigned to this post record! This should never happen ad you should never see this message, please contact support if etc... </h2>
<% else %>
<!-- Place all your current form code here -->
<% end %>