Railsters:
We have a model with 2 variables. Neither may be nil or non-nil at the
same time. They must pass this truth table:
def test_mutually_exclude
assert_equal false, Model.new.save
assert_equal false, Model.new(:thing1 => 2, :thing2 => 1).save
assert_equal true, Model.new(:thing1 => 2).save
assert_equal true, Model.new(:thing2 => 1).save
end
thing1 and thing2 default to nil. We need only one Thing at a time,
and having them both together causes trouble.
What''s the minimum set of validates_presence_of or similar validators
required to enforce this? Note the error message itself is not
important.
We have it down to 4 lines, which seems absurdly excessive for Rails,
so what are we missing?
Even better, could someone write validates_mutual_exclusivity, in the
usual 2 lines of code or less?
--
Phlip
http://www.oreilly.com/catalog/9780596510657/
"Test Driven Ajax (on Rails)"
assert_xpath, assert_javascript, & assert_ajax
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On 6/13/07, Phlip <phlip2005-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> > Railsters: > > We have a model with 2 variables. Neither may be nil or non-nil at the > same time. They must pass this truth table: > > def test_mutually_exclude > assert_equal false, Model.new.save > assert_equal false, Model.new(:thing1 => 2, :thing2 => 1).save > assert_equal true, Model.new(:thing1 => 2).save > assert_equal true, Model.new(:thing2 => 1).save > end > > thing1 and thing2 default to nil. We need only one Thing at a time, > and having them both together causes trouble. > > What''s the minimum set of validates_presence_of or similar validators > required to enforce this? Note the error message itself is not > important. > > We have it down to 4 lines, which seems absurdly excessive for Rails, > so what are we missing? > > Even better, could someone write validates_mutual_exclusivity, in the > usual 2 lines of code or less?How about something like: validates_each :thing1 do |row, attr, value| row.errors.add_to_base ''Supply thing1 or thing2, but not both'' unless value.blank? ^ row.thing2.blank? end --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
On 6/13/07, Bob Showalter <showaltb-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> How about something like: > > validates_each :thing1 do |row, attr, value| > row.errors.add_to_base ''Supply thing1 or thing2, but not both'' > unless value.blank? ^ row.thing2.blank? > end >Darned line wrapping. That "unless" part goes with the line above. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
>> Even better, could someone write validates_mutual_exclusivity, in the >> usual 2 lines of code or less? > > How about something like:validates_each :thing1 do |row, attr, value| row.errors.add_to_base ''Supply thing1 or thing2, but not both'' \ unless value.blank? ^ row.thing2.blank? end Thanks! Now I remember why I don''t twiddle bits any more! I will report back if it works. Next riddle: Our "Community Agreements" discourage ''unless''. So if you distribute a ''not'' into a boolean expression, you get if value.nil? Q value.nil?, where Q is the opposite operator from ^, right? If so, what''s Q? -- Phlip http://www.oreilly.com/catalog/9780596510657/ "Test Driven Ajax (on Rails)" assert_xpath, assert_javascript, & assert_ajax --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
On Jun 13, 2007, at 11:44 PM, Phlip wrote:>>> Even better, could someone write validates_mutual_exclusivity, in >>> the >>> usual 2 lines of code or less? >> >> How about something like: > > validates_each :thing1 do |row, attr, value| > row.errors.add_to_base ''Supply thing1 or thing2, but not both'' \ > unless value.blank? ^ row.thing2.blank? > end > > Thanks! Now I remember why I don''t twiddle bits any more! I will > report back > if it works. > > Next riddle: Our "Community Agreements" discourage ''unless''. So if you > distribute a ''not'' into a boolean expression, you get if value.nil? Q > value.nil?, where Q is the opposite operator from ^, right? If so, > what''s Q? > > -- > Phlip > http://www.oreilly.com/catalog/9780596510657/ > "Test Driven Ajax (on Rails)" > assert_xpath, assert_javascript, & assert_ajax!(a ^ b) expanding the exclusive-or !((a & !b) | (!a & b)) distribute the outer ! !(a & !b) & !(!a & b) distribute the inner !''s (!a | !(!b)) & (!(!a) | !b) simplify (!a | b) & (a | !b) and since: x & (y | z) => (x & y) | (x & z) ((!a | b) & a) | ((!a | b) & !b) ((!a & a) | (b & a)) | ((!a & !b) | (b & !b)) but: x & !x => false (false | (b & a)) | ((!a & !b) | false) and: false | y => y (b & a) | (!a & !b) and: x & y => y & x (a & b) | (!a & !b) which is equivalent to: (if you take a small hop from pure boolean algebra to Ruby) a ? b : !b so the original expression''s equivalent "if" form is: row.errors.add_to_base ''Supply thing1 or thing2, but not both'' \ if (value.blank? ? row.thing2.blank? : !row.thing2.blank?) if you look back at the original expansion of ^ [ ok, here it is: a ^ b => (a & !b) | (!a & b) ] you''ll note a similar form in the ?: expression''s equivalent: a ? !b : b If your "Community Agreements" have a similarly silly ban on the ?: expression, then don''t take the last hop (or throw the !(a^b) after the ''if''). -Rob Rob Biedenharn http://agileconsultingllc.com Rob-xa9cJyRlE0mWcWVYNo9pwxS2lgjeYSpx@public.gmane.org --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Rob Biedenharn wrote:> > validates_each :thing1 do |row, attr, value| > > row.errors.add_to_base ''Supply thing1 or thing2, but not both'' \ > > unless value.blank? ^ row.thing2.blank? > > endThat one worked.> > Next riddle: Our "Community Agreements" discourage ''unless''. So if you > > distribute a ''not'' into a boolean expression, you get if value.nil? Q > > value.nil?, where Q is the opposite operator from ^, right? If so, > > what''s Q?> row.errors.add_to_base ''Supply thing1 or thing2, but not both'' \ > if (value.blank? ? row.thing2.blank? : !row.thing2.blank?) > > if you look back at the original expansion of ^ > [ ok, here it is: a ^ b => (a & !b) | (!a & b) ] > > you''ll note a similar form in the ?: expression''s equivalent: > a ? !b : b > > If your "Community Agreements" have a similarly silly ban on the ?: > expression, then don''t take the last hop (or throw the !(a^b) after > the ''if'').Now now - someone with "agile" in their home URI should know better than to call any Community Agreement "silly". Our coding standard challenges us to reduce unless abuse, It''s still better than stating the negative at the end of an error line: errors.add "bad thing should not happen" unless good_thing() We stayed with the unless. Thanks for the math - that was awesome! -- Phlip --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
On Jun 14, 2007, at 11:19 AM, Phlip wrote:>> If your "Community Agreements" have a similarly silly ban on the ?: >> expression, then don''t take the last hop (or throw the !(a^b) after >> the ''if''). > > Now now - someone with "agile" in their home URI should know better > than to call any Community Agreement "silly". > > Our coding standard challenges us to reduce unless abuse, It''s still > better than stating the negative at the end of an error line: > > errors.add "bad thing should not happen" unless good_thing() > > We stayed with the unless. Thanks for the math - that was awesome! > > -- > PhlipGreat to see that the "standard" isn''t absolute -- I guess i read "discourage" as "prohibit". Anyway, I wouldn''t be agile if I didn''t challenge things that conflicted with my own opinions. (And ''arbitrary'' limitations on the use of language features is one of those things that I despise.) -Rob Rob Biedenharn http://agileconsultingllc.com Rob-xa9cJyRlE0mWcWVYNo9pwxS2lgjeYSpx@public.gmane.org --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---