From: Max Williams <toastkid.williams@...>
Date: 2007-11-13T00:11:50+09:00
Subject: Re: array select

Luca Roma wrote:
> i have 2 arrays of objects: dates and places
> 
> dates have attribute place_id
> and places have id
> 
> I must to selezionate all places that have id in array of objects dates.
> 
> dates.select{|obj| obj.place_id in places[].id }
> 
> How i can replace "in places[].id " to works it?
> Thanks

You could use Array#collect, which creates a new array out of another 
array, taking a block of code that processes an element of the old array 
and spits out something to go into the new array.

so,
  places[].id

would be
  places.collect{ |place| place.id}

You can then ask if obj.place_id is in this, as follows:

  dates.select{ |obj| places.collect{ |place| 
place.id}.include?(obj.place_id) }

I think that's what you're after (i'm not exactly sure from your 
question, sorry).
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