nil object - can anyone help?

rubyonrails-talk
1

Hi there,

I've been looking for a while now and can't seem to find where I'm going wrong..

I'm following a railscast tutorial to send invites out to people.

there's n invitation.rb page: class Invitation < ActiveRecord::Base   #attr_accessible :sender_id, :recipient_email, :token, :sent_at

  belongs_to :sender, :class_name => 'User'   has_one :recipient, :class_name => 'User'

  ###validation

  validates_presence_of :recipient_email   validate :recipient_is_not_registered   validate :sender_has_invitations, :if => :sender

  before_create :generate_token   before_create :decrement_sender_count, :if => :sender

private

  def recipient_is_not_registered     errors.add :recipient_email, 'Is already registered' if User.find_by_email(recipient_email)   end

  def sender_has_invitations     unless sender.invitations_limit > 0       errors.add_to_base 'You have reached your limit if invitations to send'   end

  def generate_token

    self.token = Digest::SHA1.hexdigest([Time.now, rand].join)   end

  def decrement_sender_count     sender.decrement! :invitation_limit   end end end

An invitations controller:

class InvitationsController < ApplicationController   def new     @invitation = Invitation.new   end

  def create     @invitation = Invitation.new(params[:invitation])     @invitation.sender = user     if @invitation.save       flash[:notice] = "Thanks - Invitation sent successfully."       redirect_to hub_url     else       render :action => 'new'     end   end

end

And finally, the invite count, made visible to the user:   <% if @user.invitation_limit > 0 %>             <%= link_to 'Send invitation!', new_invitation_path %>

            <% end %>

THis page, for some odd reason will not render. Instead I get: You have a nil object when you didn't expect it! The error occurred while evaluating nil.>

Can anyone see the obvious mistake? I could do with a fresh pair of eyes on this... :slight_smile:

Thanks a lot!

2

In your view you're accessing the instance variable @user, but you're not setting that anywhere in your controller (at least in the code you've posted). So when your view renders, the @user variable is nil... possibly the error.

3

Craig Westmoreland wrote:

THis page, for some odd reason will not render. Instead I get: You have a nil object when you didn't expect it! The error occurred while evaluating nil.>

Can anyone see the obvious mistake? I could do with a fresh pair of eyes on this... :slight_smile:

Have you looked at your stack trace to see where your app encounters the nil object? The stack trace should direct you to the line in the file causing the problem.

4

yeah - it's complaining about the @user in

    <% if @user.invitation_limit > 0 %>             <%= link_to 'Send invitation!', new_invitation_path %>

            <% end %>

I've tried renaming it with just user, then User, but i can't seem to get my head around this..

Any ideas?

Many thanks..

5

I don’t see you defining @user anywhere. Which view is your code in?

6

my view is in the main layouts file.

I also tried to add @invitation.sender = @user to the invitations controller but that hasn't solved it...

7

Your application.html.erb?

Then yeah, you’re going to need @user defined in every controller.

Also, is this a user that was created before you added in your invitations? If so, you won’t have anything for an invitation_limit for any of your users, you’ll want to do a User.all.each{|user| user.invitation_limit = 5 && user.save } to give them the ability to send invitations. The after_create handles it for new users only.

8

in that case, would it make more sense to add it to a page when a user is already logged in?

I've just tried adding it to the invitation's index page, and i get the same issue...

sorry....

9

Craig Westmoreland wrote:

my view is in the main layouts file.

I also tried to add @invitation.sender = @user to the invitations controller but that hasn't solved it...

Of course. It's @user that's coming up nil in the first place.

Best,

10

Craig Westmoreland wrote:

in that case, would it make more sense to add it to a page when a user is already logged in?

Heck yes.

I've just tried adding it to the invitation's index page, and i get the same issue...

sorry....

Best,

11

If you're following a Railscast, I don't know where you may be going wrong, because I've always found them to be very methodical. It may be that you've missed a step, or put something in the wrong place.

I'd suggest you backtrack, and follow the tutorial from the start again - after all, they're only 10mins long.

Also, inferring from your misunderstanding of the assignments and variable scopes (and of course that you say you're a Rails newbie), you might benefit from refreshing yourself of some of basic principles covered in the "getting started" chapter of your favourite Rails book.

12

Hmmm..

It's still not working, even when I've added it in the invitations view page.

:frowning:

13

ok -

i've managed to get the following to render correctly (from within the application.html.erb file:

            <% if @user.invitation_limit > 0 %>             <%= link_to 'Send invite', :controller => 'invitations', :action => 'new' %>

            (<%= @user.invitation_limit %> left)

              <% end %>

However, when the link is clicked (send invite), I now get the error mentioned before:

You have a nil object when you didn't expect it! The error occurred while evaluating nil.invitation_limit

Any ideas where i need to make the change now, so this works?

Thanks again...

14

considering it’s user.invitation_limit, (or maybe @user), that means you need to define one or the other.

15

Yeah - I have @ user defined in the view and the controller....

16

Are you defining @user in application_controller.rb? I don't see it defined anywhere in the code you posted. If you're using an authentication plugin, you probably want to do something like:

@user = current_user

Even then, you'll have to check to see if current_user is nil, unless that page is only visible to logged in users. You can do this with something like:

<% if @user && @user.invitation_limit > 0 %>

Also, in your create method you'll want to do something like:

@invitation.sender = @user

or

@invitation.sender = current_user

Jarin Udom Robot Mode LLC

17

cool thank you.

All valid points... I think i'll go through the tutorial again. I may have missed something.

cheers