# Sorting different objects **URL:** \ **Category:** Rails\ **Created:** [September 17, 2007, 1:24pm UTC](https://www.ruby-forum.com/t/sorting-different-objects/114669 "2007-09-17T13:24:00Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Iain\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/6bbea6/32.png) [@Iain\_A](https://www.ruby-forum.com/u/Iain_A)\ **Post date:** [September 17, 2007, 1:24pm UTC](https://www.ruby-forum.com/t/sorting-different-objects/114669/1 "2007-09-17T13:24:00Z")
hi I have an array of topics and posts each has an updated\_on field. I want to sort the array so in the order of the updated\_on field. I.e 1 Topic updated on 5 march 2 Poll updated on 4 march 3 Topic updated on 6 march 4 poll updated on 7 march shoud go 4,3,1,2 my code looks like this @topicsAndPolls.sort { |a,b| a.updated\_on \<=\> b.updated\_on} but this isnt working. Do I have to define the \<=\> method somewhere. Can I pass that in the block aswell? Thanks Iain A. ---
**Author:** ![Iain\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/6bbea6/32.png) [@Iain\_A](https://www.ruby-forum.com/u/Iain_A)\ **Post date:** [September 25, 2007, 11:01pm UTC](https://www.ruby-forum.com/t/sorting-different-objects/114669/2 "2007-09-25T23:01:24Z")
On Fri, 14 Sep 2007, Iain A. wrote: > I have an array of topics and posts each has an updated\_on field. I > want to sort the array so in the order of the updated\_on field. > […] > my code looks like this > @topicsAndPolls.sort { |a,b| a.updated\_on \<=\> b.updated\_on} > [\n inserted] but this > isnt working. Do I have to define the \<=\> method somewhere. Can I pass What do you assign the result of this to? Or did you mean @topicsAndPolls.sort! { |a,b| a.updated\_on \<=\> b.updated\_on} ? That’s s/sort/sort!/ in sed parlance, in case the addition of one char is as hard for you to spot as for me. > that in the block aswell? If updated\_on returns a Date then \<=\> should work. If it doesn’t you’ll get a NoMethodError. ``` Hugh ``` ---
**Author:** ![Iain\_A](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/6bbea6/32.png) [@Iain\_A](https://www.ruby-forum.com/u/Iain_A)\ **Post date:** [September 25, 2007, 11:03pm UTC](https://www.ruby-forum.com/t/sorting-different-objects/114669/3 "2007-09-25T23:03:10Z")
> shoud go 4,3,1,2 > > my code looks like this > @topicsAndPolls.sort { |a,b| a.updated\_on \<=\> b.updated\_on} but this > isnt working. Do I have to define the \<=\> method somewhere. Can I pass > that in the block aswell? In addition to the other reply, you’re looking for a descendant sort… so you really want: { |a,b| b.updated\_on \<=\> a.updated\_on} (not the switching of a and b) -philip