From: Ezra Zygmuntowicz <ezmobius@...>
Date: 2007-07-12T06:00:08+09:00
Subject: Re: Returning part of a hash


On Jul 11, 2007, at 1:30 PM, barjunk wrote:

> I have hash that has about 20 keys.  I'd like to create a new variable
> with just three of those keys.  Example:
>
> hash = { "key1" => "value1",
>                "key2" => "value2",
>                ...
>                "key20" => "value20" }
>
> And a function like:
> newhash = hash.slice("key2","key5","key7")
>
> Which creates:
>
> newhash = { "key2" => "value1",
>                "key5" => "value5",
>                "key7" => "value7" }
>
> hash.select {|key, value| key == "key1" }
>
> I could do the above multiple times, but this returns an array not the
> hash pair.
>
> Thanks for any help.
>
> Mike B.


Hey Mike-

	Here are two handy methods for doing what you want:

class Hash
   # lets through the keys in the argument
   # >> {:one => 1, :two => 2, :three => 3}.pass(:one)
   # => {:one=>1}
   def pass(*keys)
     self.reject { |k,v| ! keys.include?(k) }
   end

   # blocks the keys in the arguments
   # >> {:one => 1, :two => 2, :three => 3}.block(:one)
   # => {:two=>2, :three=>3}
   def block(*keys)
     self.reject { |k,v| keys.include?(k) }
   end

end


Cheers-

-- Ezra Zygmuntowicz 
-- Lead Rails Evangelist
-- ez@engineyard.com
-- Engine Yard, Serious Rails Hosting
-- (866) 518-YARD (9273)