Chaining & to_proc on symbol

Question

It\'s well known to Rubyist & will call to_proc on a symbol, so

[:a, :b, :c].map(&:to_s)

is equivalent to

Answer 1

So just for fun (and to prove that almost anything is possible in ruby if one puts in a bit of effort) we could define a method on Symbol (we'll call it Symbol#chain) to provide this functionality and a little more

class Symbol
  def proc_chain(*args)
    args.inject(self.to_proc) do |memo,meth|
      meth, *passable_args = [meth].flatten
      passable_block = passable_args.pop if passable_args.last.is_a?(Proc)
      Proc.new do |obj|
        memo.call(obj).__send__(meth,*passable_args,&passable_block)
      end
    end
  end
  alias_method :chain, :proc_chain
end

This can then be called like so

[:a, :b, :c].map(&:to_s.chain(:upcase))
#=> ["A","B","C"]
# Or with Arguments & blocks
[1,2,3,4,5].map(&:itself.chain([:to_s,2],:chars,[:map,->(e){ "#{e}!!!!"}]))
#=>  => [["1!!!!"], ["1!!!!", "0!!!!"], ["1!!!!", "1!!!!"],
#        ["1!!!!","0!!!!", "0!!!!"], ["1!!!!", "0!!!!", "1!!!!"]]

Can even be used as a standalone

p = :to_s.chain([:split,'.'])
p.call(123.45)
#=> ["123","45"]
# Or even 
[123.45,76.75].map(&p)
#=> => [["123", "45"], ["76", "75"]]