On Aug 20, 2009, at 11:58 PM, [email protected] wrote:
> 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.
>
> any takers on this one?
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?"
class Quote
belongs_to :original, :class_name => 'Quote'
has_many :requotes, :class_name => 'Quote', :foreign_key => :original
def requoted?
!self.original.nil?
end
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.
-Rob
Rob Biedenharn http://agileconsultingllc.com
[email protected]
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