From: Chris Shea <cmshea@...>
Date: 2007-07-12T05:50:01+09:00
Subject: Re: Returning part of a hash

On Jul 11, 2:28 pm, barjunk <barj...@attglobal.net> 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.

This works:

class Hash
  def slice(*args)
    sliced = self.dup
    sliced.delete_if {|k,v| not args.include?(k)}
  end
end

Or you could do this:

class Hash
  def slice(*args)
    ret = {}
    args.each {|key| ret[key] = self[key]}
    ret
  end
end

I'm sure there are other ways.

HTH,
Chris