ActiveRecord: find_or_create with has_and_belongs_to_many -- unexpected behavior

ruby-talk
1

I am attempting to use find_or_create on a foreign table with a has_and_belongs_to_many relationship with my current table. I am doing the following:

term = school.terms.find_or_create_by_code("FALL06")

the queries in the log show the expected SELECT statement to query if there is a join table record between the school and term with code "FALL06":

SELECT * FROM term
INNER JOIN school_term ON term.id = school_term.term_id
WHERE (school_term.school_id = 1 )
   AND (term.`code` = 'FALL06' )
LIMIT 1

but the INSERT behavior does not include a join table insert if the SELECT does not find an appropriate record:

INSERT INTO term (`code`, `name_full`, `name_common`, `date_end`, `date_start`)
VALUES('FALL06', NULL, NULL, NULL, NULL)

I have resolved this by changing my original code to implement a uniqueness check in ruby:

term = school.terms.find_or_create_by_code("FALL06")
school.terms << term unless school.terms.any? do |i| i == term;

It seems like ActiveRecord and SQL should take care of that behavior rather than the ActiveRecord implementor and Ruby. Am I missing something? Is there another way to do what I want?

Also, I'm not sure if c.l.ruby is the best newsgroup, but I couldn't find a ruby on rails group.

Thanks Sincerely,
Red Daly

2

Also, I'm not sure if c.l.ruby is the best newsgroup, but I couldn't find a ruby on rails group.

You want the rails mailing list:
http://lists.rubyonrails.org/mailman/listinfo/rails

If you don't want to deal with lots of email traffic, there a web gateway to it at

···

On Aug 1, 2006, at 10:25 AM, Red Daly wrote:

Thanks Sincerely,
Red Daly