From: "David A. Black" <dblack@...>
Date: 2008-07-22T20:22:21+09:00
Subject: Re: Grouping/Sorting an Array of objects

Hi --

On Mon, 21 Jul 2008, Howard Roberts wrote:

> Suppose I have an array of two different kinds of objects, each with
> different attributes, but both having a date attribute. I'd like to be
> able to loop through the array in such a manner as to be able print a
> result similar to the following:
>
>
> 07/19/08
>   Foo-1 - Name
>     attr 1
>     attr 2
>     [..]
>
>   Foo-2 - Name
>     attr 1
>     attr 2
>     [..]
>
>   Bar - Name
>     attr 1
>     attr 2
>     [..]
> 07/20/08
>  Foo-1 - Name
>     attr 1
>     attr 2
>     [..]
>
>  Bar - Name
>     attr 1
>     attr 2
>     [..]
> etc.
>
> showing all of the Foo's first, then the Bar's, for each date.
> If I only have Foo's, I can easily do:
>
> @data.sort{|x,y| Time.parse(x.date) <=> Time.parse(y.date)}).each do
> |foo|
>  puts Foo.date # Still shows date on each loop, but okay
>  puts Foo.name
>  [..]
> end
>
> To get things in date order, but when I consider mixing a second object
> into the array, that confounds matters for me. I suspect group_by{|item|
> item.class} may be part of the solution, but I'm not sure how?
>
> Any pointers would be most appreciated.

Here's a stab at it: http://pastie.org/238521. I've put the sorting
intelligence in the objects, and also given them to_s methods so you
don't have to do all that formatting in the calling code (though you
can, of course, if you want a different output).

The last ten lines still seem a bit wordy to me but so be it; I have
to go get ready for work :-)


David

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