I have a post model which has_many comments and a comment model which belongs_to a user and I am looping through the comments trying to get the users information. if i do comment.user.to_yaml I can see all of the attributes but when I try to get the usern

gistfile1.rb

show.html.slim

  - @post.comments.each do |comment|  
    div.comment
      # Works and shows user attributes

      / --- !ruby/object:User 
      / aggregation_cache: {}
      / 
      / association_cache: {}
      / 
      / attributes: 
      /   id: 17
      /   username: andrew
      /   email: xxx@gmail.com
      /   created_at: 2011-12-07 15:28:11.556687
      /   updated_at: 2011-12-07 15:28:11.556687
      /   password_digest: xxx
      /   avatar: 
      / attributes_cache: {}
      / 
      / changed_attributes: {}
      / 
      / destroyed: false
      / marked_for_destruction: false
      / new_record: false
      / previously_changed: {}
      / 
      / readonly: false
      / relation:

      = comment.user.to_yaml
      # Doesn't work and gives error: undefined method `username' for nil:NilClass
      = comment.user.username
      = comment.body

comment.rb

class Comment < ActiveRecord::Base
  belongs_to :user
  belongs_to :post, counter_cache: :comment_count
end

user.rb


class User < ActiveRecord::Base

  mount_uploader :avatar, ImageUploader

  attr_accessible :email, :username, :password, :password_confirmation, :avatar
  
  has_secure_password
  has_many :posts
  has_many :authentications
  has_many :comments

  validates :username, presence: true, 
                       uniqueness: true,
                       length: { in: 4..20 }

  validates :email, presence: true,
                    uniqueness: true,
                    format: { with: /^([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})$/i }

  validates :password, presence: true, on: :create

  def self.find_by_email_or_username (email_or_username)
    where('email = ? OR username = ?', email_or_username, email_or_username).first
  end

  def setup_omniauth(omniauth)
    self.username = omniauth[:info][:nickname] if omniauth[:info][:nickname]
    self.email    = omniauth[:info][:email] if omniauth[:info][:email]
  end

  def apply_omniauth(omniauth)
    authentications.build(provider: omniauth[:provider], uid: omniauth[:uid])
    self.remote_avatar_url = omniauth[:info][:image] if omniauth[:info][:image] && !avatar
  end
  
  def to_param
    username.parameterize
  end

end