Hi Matt/all,
Actually from what I can see Rails does not hold off on trigger it's
"after_save" callbacks until just before commit in the case they are wrapped
in a specific transaction (unfortunately). So there's still no
"before_commit" equivalent yet anyone has identified. Let me know if I'm
wrong however here's the test I've run.
------------------- test output
-------------------------------------------------
Macintosh-2:after_create_test greg$ spec
spec/model/with_transaction_block.rb
BOOK: before_save
F
1)
RuntimeError in 'Book should allow creation of book-allocation-chapter if
costs match'
amounts do NOT match
./spec/model/with_transaction_block.rb:27:in `after_save_check'
./spec/model/with_transaction_block.rb:57:
./spec/model/with_transaction_block.rb:56:
Finished in 0.048817 seconds
1 example, 1 failure
Macintosh-2:after_create_test greg$
--------------- spec
------------------------------------------------------------------
require File.expand_path(File.dirname(__FILE__) + '/../spec_helper')
# ------------ ALLOCATION -------------
class Allocation < ActiveRecord::Base
belongs_to :book
belongs_to :chapter
before_save :after_save_check
def after_save_check
puts "ALLOCATION: before_save"
b = self.book
sum = b.allocations.sum(:amount)
raise("amounts do NOT match") if !(b.amount == sum)
end
end
# ----------- BOOK ---------------
class Book < ActiveRecord::Base
has_many :allocations
has_many :chapters, :through => :allocations
before_save :after_save_check
def after_save_check
puts "BOOK: before_save"
sum = self.allocations.sum(:amount)
raise "amounts do NOT match" if !(self.amount == sum)
end
end
# ----------- CHAPTER ---------------
class Chapter < ActiveRecord::Base
has_many :allocations
has_many :books, :through => :allocations
before_save :after_save_check
def after_save_check
puts "CHAPTER: before_save"
end
end
# --------- RSPEC (BOOK) ------------
describe Book do
before(:each) do
@b = Book.new(:amount => 100)
@c = Chapter.new()
end
it "should allow creation of book-allocation-chapter if costs match" do
Book.transaction do
@b.save! # SEEMS TO TRIGGER BOOK AFTER_SAVE HERE RATHER THAN HOLDING
OFF
@c.save!
@a1 = Allocation.create!(:book_id => @b.id, :chapter_id => @c.id,
:amount => 100)
end
end
end
-------mysql log
-----------------------------------------------------------------
090125 15:31:46 1534 Connect r...@localhost on after_create_test_test
1534 Query SET SQL_AUTO_IS_NULL=0
1534 Statistics
1534 Query SHOW FIELDS FROM `books`
1534 Query SHOW FIELDS FROM `chapters`
1534 Query BEGIN
1534 Query SHOW FIELDS FROM `allocations`
1534 Query SELECT sum(`allocations`.amount) AS
sum_amount FROM `allocations` WHERE (`allocations`.book_id = NULL)
1534 Query ROLLBACK
1534 Quit
Is my analysis correct?
Cheers
Greg
On Sun, Jan 25, 2009 at 10:08 AM, Matt Jones <[email protected]> wrote:
>
> There's no explicit hook, but you can pretty much do what you've
> described using transactions.
> If you're updating the chapters in a single controller action, you can
> use a transaction block
> (see
> http://api.rubyonrails.org/classes/ActiveRecord/Transactions/ClassMethods.html
> )
> to wrap all
> the changes. Then, either use an after_save on Book, or just call a
> method directly to validate the
> combination.
>
> You'll want to use save! and friends within the block, and catch
> exceptions (ActiveRecord::RecordInvalid and
> ActiveRecord::RecordNotSaved) to display errors.
>
> --Matt Jones
>
>
> On Jan 24, 2009, at 6:44 PM, Greg Hauptmann wrote:
>
> > Hi Mike, all
> >
> > Understood. To help align my fictitious example to the cross-model
> > validation question I've asked consider that:
> > (a) the book value is fixed [e.g. perhaps think of this as a bank
> > account transaction amount, being allocated out to different tax
> > categories & then the user wants to adjust the tax categories]
> > (b) the user manually adjusts the chapter value (i.e. there is no
> > programmatic approach to calculating the distribution)
> >
> > So this brings it back to my scenario I'm not sure how to solve in
> > Rails whereby the sequence of events here would be:
> > - change chapter 1 value
> > - change chapter 2 value
> > - change chapter 3 value
> > - <only at this point should the cross model business rule be
> > checked, i.e. Book.amount.should == Sum(chapter values)>
> >
> > My assumption here (correct me if I'm wrong) is that any Rails
> > validation/after_save/observer kicks in at such of the sequence
> > points, whereas what is actually required here is a cross_model
> > business logic check at the end.
> >
> > Does this make sense? Is there a ways in Rails to get access to a
> > "before_commit" type hook that would align with the point I want the
> > business logic check to kick in?
> >
> > Thanks
> >
>
>
> >
>
--
Greg
http://blog.gregnet.org/
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