From: Howard Roberts <howardroberts@...>
Date: 2008-07-21T12:23:34+09:00
Subject: Grouping/Sorting an Array of objects

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.

Thanks,
Howard
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