From: Craig Demyanovich <cdemyanovich@...>
Date: 2007-07-12T06:35:01+09:00
Subject: Re: Returning part of a hash

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On 7/11/07, Craig Demyanovich <cdemyanovich@gmail.com> wrote:
>
> On 7/11/07, Ezra Zygmuntowicz <ezmobius@gmail.com> wrote:
>
> >
> > 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
>
>
> Ezra,
>
> Since you're adding the #pass and #block methods to Hash and Hash already
> has a #keys method, is there a conflict between the *keys parameter to #pass
> and #block and the #keys method on Hash?
>
> Thanks,
> Craig
>
>
> To answer my own question (wasn't sure I'd have time before leaving),
there's no conflict. The methods worked as advertised in my irb session just
now.

Craig

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