From: Chris Shea <cmshea@...>
Date: 2008-11-18T08:51:32+09:00
Subject: Re: function to select only certain key/value pairs from hash?

On Nov 17, 4:46 pm, Chris Shea <cms...@gmail.com> wrote:
> On Nov 17, 3:50 pm, Aryk Grosz <tennisbum2...@hotmail.com> wrote:
>
>
>
> > Whenever Im coding I usually come across having to create a new hash
> > from the key/value pairs of another hash.
>
> > For example,
>
> > hash = {:a => 1, :b => 2, :c => 3}
>
> > I want to do something like this
>
> > hash.from_keys(:a,:b) => {:a=> 1, :b=> 2}
>
> > Is there something like this already? Perhaps in the facets library? I
> > looked and couldn't find anything.
>
> > If anybody thinks that I shouldnt even be getting into this situation in
> > the first place, please let me know that as well.
> > --
> > Posted viahttp://www.ruby-forum.com/.
>
> Hmm... I thought there was a built in method for that.  Here's one
> way:
>
> hash = {:a => 1, :b => 2, :c => 3}
> Hash[*hash.select {|k,v| [:a,:b].include?(k)}.flatten]  #=>
> {:b=>2, :a=>1}
>
> HTH,
> Chris

Yeah, or the simpler: hash.reject {|k,v| ![:a,:b].include?(k)}