From: Robert Klemme <shortcutter@...>
Date: 2006-06-23T23:47:29+09:00
Subject: Re: Turning an Array into a Hash based on an attribute value

2006/6/22, Ashley Moran <work@ashleymoran.me.uk>:
>
> On Jun 22, 2006, at 8:25 pm, Simen Edvardsen wrote:
> > Hash[*self.map{|m|m.send(method).to_s.to_sym}.zip(self).flatten ]
>
> > Disclaimer: inject is probably more appropriate, but my solution at
> > least looks cooler ;)
>
> Simen... you don't come from a Perl background do you ;)

LOL - Could also be awk - because the code looks so awkward. :-))

> On Jun 22, 2006, at 8:09 pm, Simon Kr�ger wrote:
> > class Array
> >   def hash_on(method)
> >     inject({}){|h, i| h.merge({i.send(method).to_s.to_sym, i})}
> >   end
> > end
>
> I like!

I like Robin's inject solution more - it's more efficient and avoids
all those short lived hash objects.  Also, I'd put it into Enumerable,
 add a block and provide a list of args instead of the method name
only:

module Enumerable
  def to_hash(*args,&b)
    inject({}) {|h,e| h[b ? b[e] : e.send(*args)] = e; h}
  end
end

irb(main):019:0> %w{foo bar baz}.to_hash {|x| x[0]}
=> {102=>"foo", 98=>"baz"}
irb(main):020:0> %w{foo bar baz}.to_hash(:[], 0)
=> {102=>"foo", 98=>"baz"}

# silly example to demonstrate what you cannot do without a block
irb(main):022:0> %w{foo bar baz}.to_hash {|x| x.length * rand(100)}
=> {132=>"bar", 15=>"foo", 186=>"baz"}

> Incidentally... what is the convention here on CCing posters in
> replies?  I come from the FreeBSD lists where it's normal to CC the
> poster so they don't have to check the list.  But people on Ruby
> lists are really surprised when I do that.

I usually don't because I assume people are checking thelist anyway -
and until now nobody has complaint that he / she missed a posting from
me. :-)

Kind regards

robert



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