Maybe I'm looking at this the wrong way and with that - hopefully
someone can either suggest a simpler way or the right way.
I have a Quote model - for all intents and purposes, just say it has
one attribute :price.
I want to be able to add the following self-referential attributes
(which I *think* should be under a has_many, through)
Quotes
has_many requotes through... something
When a quote is made it's attached to a specific job and locked. When
a similar job comes in, I want to take the original quote, duplicate
it and update it to match the specs of the new job; the old quote
still intact and both having a knowledge of their "parent-child"
relationship.
I've looked at Ryan Bates latest railscast on self referential
relationships but that doesn't seem to solve the whole problem.
Say I have quote_id 3 which has been requoted 3 different times. I
then go back and requote one of those, say quote #4.. (check the
"hopefully understandable" chart below)
quote#3
=quote#4
==quote#7
=quote#5
=quote#6
quote 3 has 3 children and its first child has a child.
now say I delete quote 4... quote 7 doesn't know who its proverbial
daddy is. and quote 3 doesn't know it has any grandchildren. in
theory, i'd like 3&7 to link up when the link between them breaks.
Well, it's true that #4 knows its original, but #3 only knows about the requotes by asking, in effect, "Hey, I'm #3. Which of you quotes are requotes from me?"
def requote
raise "Oops! Can't requote an unsaved Quote" if self.new_record?
child = self.clone
child.original = self.id
end
end
three = Quote.new(:price => 1.00) {|q| q.id = 3 }
three.save
four = three.requote; four.save
five = three.requote; five.save
six = three.requote; six.save
seven = four.requote; seven.save
OK, now then, is four.destroy allowed? (meaning does the business thing exist in such a way that it is OK?)
You might want to have a before_destroy callback that prevents a quote from being removed if it has been requoted.
class Quote
before_destroy :ensure_no_requotes # placed earlier than the has_many
protected
def ensure_no_requotes
self.requotes.empty?
end
end
Alternatively, you could treat the chain of requotes as a linked-list and
self.requotes.each {|r|r.original = self.original; r.save}
in an after_destroy callback perhaps.
