Is there a way to specify a possible relationship between mo

My app allows users to register and login but it also allows anyone to
add
comments, regardless of whether they are registered or not.

I have a comment table and a user table and I’d like to store the name
and
home page url of the comment author.

If the user is registered, then the comment needs a foreign key back to
the
registered user. But if the comment was posted anonymously, then I need
to
record the author name and url directly in the comment table. My
comments
table ends up with both:

class CreateComments < ActiveRecord::Migration
def self.up
create_table :comments do |t|
t.column :comment, :text
t.column :article_id, :integer
t.column :user_name, :string #only used if user_id is empty
t.column :user_url, :string #only used if user_id is empty
t.column :user_id, :integer #when populated, user_name and
user_url
are ignored
end
end

def self.down
drop_table :comments
end
end

Then in my code when I need to find the author of the comment, I check
the
comment’s user_id and either get the author from the user record
(user.name)
or from the comment directly (user_name).

My question: Does rails have any mechanism for automatically getting the
data either from a foreign key or directly from the record? Such a
mechanism
would save me from checking the foreign key to determine where the data
should come from. Or perhaps there is a better database design for this
situation?

Cheers

end
My question: Does rails have any mechanism for automatically getting the
data either from a foreign key or directly from the record? Such a mechanism
would save me from checking the foreign key to determine where the data
should come from. Or perhaps there is a better database design for this
situation?

You could override Comments#user to do the check for you automatically.
That might get you into trouble though for an unregistered users if you
forget.

But that’s probably the easiest way to “hide it” from yourself…

-philip

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