ActiveRecord#create and associations

Rails
1

This is a dumb question, but I just want to double check and can’t find
an explicit reference online…

#So. say I have

class Person < ActiveRecord::Base

belongs_to :phonebook
…
end

#Let’s say I have pb = to an instance of PhoneBook, then

#will this in general work?

x = Person.create(:phonebook => pb, …)

or do I have to do this:

x = Person.create(…)
x.phonebook = pb
x.save!

or this:

x = Person.create(:phonebook_id => pb.id, …)

Thanks!

– Pito

2

Yes, either of those will work. Assuming Phonebook has_many :people as
well,
you should also be able to do:

pb.people.create(…)

The rails console is a great way to test these out and see if they will
work
within a few moments… :slight_smile:

Phil

3

the way to usually do it is ,

@person.phonebooks.new(params[:phonebook])

it will automatically associates the phonebook to the user, it is also
an
easy way of accessing associations in test.

4

Thanks… And the reason:

x = Person.create(:phonebook => pb, …)

does not work is that the hash params for create have to be actual
attributes of the model, and not associations?

– Pito

5

On Thu, Feb 10, 2011 at 12:03 PM, Pito S. [email protected]
wrote:

Thanks… And the reason:

x = Person.create(:phonebook => pb, …)

does not work is that the hash params for create have to be actual
attributes of the model, and not associations?

It will work. You can do it any one of the ways that were mentioned.

redhames example is of creating a phonebook when you already have a
Person;
I thought you were speaking of creating a Person when you already have a
Phonebook (pb) …? At any rate, all these example will work fine. Use
the
one that makes the most sense to you. :slight_smile:

6

x = Person.create(:phonebook => pb, …)

does not work is that the hash params for create have to be actual
attributes of the model, and not associations?

It will work. You can do it any one of the ways that were mentioned.

Hmm, my test in script/console has it not working unless I specify the
‘id’, that is, unless I do this:

specify id explicitly:

x = Person.create(:phonebook_id => pb.id)
x.save # works

but

rely on association:

x = Person.create(:phonebook => pb, …)
x.save # fails with a validation error: phonebook cannot be blank

is something more/or else messed up?

Pito

7

On Thu, Feb 10, 2011 at 12:52 PM, Pito S. [email protected]
wrote:

‘id’, that is, unless I do this:
is something more/or else messed up?

Here’s a guess, after relooking over your code above. The problem could
naming conventions.

When you say belongs_to :phonebook, Rails expects to look for a class
named
Phonebook (lowercase ‘b’), not PhoneBook

If your model is named PhoneBook, the association should be: belongs_to
:phone_book

You can override the default behavior with something like:
belongs_to :phonebook, :class_name => ‘PhoneBook’
but it’s usually easier to do things the way Rails expects them to be
done,
unless there is an important reason to use different naming conventions.

Unless your model is not really PhoneBook…? the point is, the
difference
between PhoneBook and Phonebook, and phonebook or phone_book, is
actually significant, and will cause you bugs and headaches if you
don’t
use the one rails will use by default.