rails "undefined method" error inside loop which is not evaluated

Question

This code works properly (using HAML):

#comments
  - @blog.comments.each do |comment|
    .comment
      .username
        - if !eval("comment.user").nil?
          #{comment.user.email}
      .content
        #{comment.content}

However, if I remove the "eval" line i.e.

#comments
  - @blog.comments.each do |comment|
    .comment
      .username
        #{comment.user.email}
      .content
        #{comment.content}

I get an error:

undefined method `email' for nil:NilClass

Even when there are no comments in the database (hence the loop contents should not be evaluated). What is going on?

- if !eval("comment.user").nil? this is ugly, just use - if comment.user — Mikhail Nikalyukin
– Mikhail Nikalyukin, Commented Jan 23, 2012 at 13:54
@MikhailNikalyukin thx, I was looking for some cleaner syntax. I thought I tried that before, but it works now :) — Jonathan Maddison
– Jonathan Maddison, Commented Jan 23, 2012 at 16:45

carpamon · Accepted Answer · 2012-01-23 16:03:34Z

1

Try the following:

#comments
  - @blog.comments.each do |comment|
    .comment
      .username
        - if comment.user
          = comment.user.email
      .content
        = comment.content

I think the problem is that you are forcing ruby to evaluate comment.user.email with #{comment.user.email}.

Try this in the console:

def fail(param)
  if param
    puts "hello #{1/0}"
  end
end

fail(nil)

It will fail because of a division by 0, but param is nil.

edited Jan 23, 2012 at 16:03

answered Jan 23, 2012 at 13:53

carpamon

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2 Comments

Romain Over a year ago

The OP is asking why he's getting the nil.email bug whereas @blog.comments should be empty, since the comments table is empty in his DB (or so he says ;))

Jonathan Maddison Over a year ago

thx, but I believe I've had this issue in ERB templates too (without using ${} syntax)

Jonathan Maddison · Accepted Answer · 2012-01-23 16:39:39Z

1

Ah, problem solved!

Issue was that above the posted code, I had the line:

= form_for @blog.comments.build, :remote => true do |f|

When I moved that form below the loop the error disappeared.

answered Jan 23, 2012 at 16:39

Jonathan Maddison

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