Rails help create has many and belongs to assoction

Here is m开发者_C百科y user model:

class User < ActiveRecord::Base
has_many :posts
end

Here is my post model:

class Post < ActiveRecord::Base
before_create :ejer
belongs_to :user
def ejer
    self.user.build
end
end

I am using devise and when I have signed in and trying to create a post i gets this error:

NoMethodError in PostsController#create

undefined method `build' for nil:NilClass

I have created a column user_id in posts table.

Why do I get the error and how do I assoctie current user that is signed in with the post?

---

self.user will be nil so you're trying to run the method build on nil which will raise an exception like you're getting.

To add a user to the post you can just assign it by setting the attribute:

def ejer
  self.user = User.new
end

You could also use the build_user method

def ejer
  build_user
end

Or set the user to an existing user:

def ejer
  self.user = User.first
end

---

Judging by your comments in response to Mario you don't actually want to build a new user - that would create a new record.

I recommend taking a look at the sentient_user gem. Once you've hooked it up correctly in the models and controllers your posts model can become:

class Post < ActiveRecord::Base

  belongs_to :user
  validates :user, :presence => true

  before_validate do
    self.user ||= User.current_user
  end
end

I changed the hook to be before_validate and added a validation to ensure that there is a user associated since in most cases it doesn't make sense to allow a post to be created without a user id.

(oh and I'm sure there are other solutions to getting a User.current_user or equivalent, sentient_user is just the one I personally use.)