From: Jason Leong <jason@...>
Date: 2008-11-03T09:00:15+09:00
Subject: Re: Indexed arrays, delete_if, and performance

 > Please look carefully at the code.  Although untested it should do
> exactly this: delete from the other Hash.  Note that the return value of
> Hash#delete is the deleted element.  I probably should have added a
> safety check to ensure nil does not cause errors.  So you'd probably
> rather do
> 
>    def delete_by_id(id)
>      dlt = @ev_by_id.delete(id) and dlt.each do |ev|
>        @ev_by_date[ev.date].delete(ev)
>      end
>    end

Ah yes! Pounded off a reply before I looked, sorry - thanks for the 
safety check too, that certainly came in handy. The one difference in my 
final implementation is this:

  def delete_events_by_id(id)
    dlt = @titles.delete(id.to_i) and dlt.each do |e|
      @events[e.date].delete_if { |i| i.id == e.id }
    end
  end

The reason being (I think!) the object passed in for deletion in 
@ev_by_date[ev.date].delete(ev) does not match up with the object in 
@ev_by_date as they're two different Hashes - but a compare based on the 
id works. Does that sound right?

Thanks Robert, you've taught me a bunch about Hashes!
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