Building associations

Rails
1

I have a model with has_many (not :through) and am adding members to
it like this:

class Panda < AR::Base
has_many :baby_bears, :after_add => :increment_baby_count

def do_it
self.baby_bears << BabyBear.create({:name => “Fluffy”})
end
end

In looking at the log, this results in 2 SQL statements, an INSERT
(for the create) immediately followed by an UPDATE of the same record
(no changes were made!).

If I look in vendor/rails/active_record/lib/active_record/associations/
has_many_associations.rb#insert_record

which handles the over-loading of the “<<” method I can see that it is
blindly calling “record.save”, which is the cause of the UPDATE. In
this case its the perfect situation for ActiveRecord supporting a
“dirty” bit.

However, I think that I am not doing this correctly. That is, I am not
adding my association member correctly.

If I use “self.baby_bears.create({:name => “Fluffy”})” then
my :after_add callback does NOT get called, but it does get called in
the first method.

In summary:

How do I add an association member that does not generate 2 SQL
statements AND get my :after_add callback executed?

Thanks in advance.

2

Wiliam Langshaw wrote:

How do I add an association member that does not generate 2 SQL
statements AND get my :after_add callback executed?

What about

self.baby_bears << BabyBear.new(:name => "Fluffy")

–
We develop, watch us RoR, in numbers too big to ignore.

3

or simply

self.baby_bears.create(:name => “Fluffy”)

4

Yup, thats the ticket, using “new” versus “create”. I should have
thought of that before, I feel like an idiot!

@Thorsten: your idea of

self.baby_bears.create(:name => “Fluffy”)

does not (completely) work because the :after_add callback is not
being triggered.

Thanks!