From: Arturo Garcia <arturo.g.arturo@...>
Date: 2010-11-26T23:11:45+09:00
Subject: Re: Newbie: two cool discoveries

the "&" is a shortcut to "to_proc"

class Symbol
  def to_proc
    lambda { |x| x.__send__(self) }
  end
end

So in theory, you could use to send *any* message

( Ruby 1.9* btw )


On Friday 26 November 2010 14:00:15 Diego Virasoro wrote:
> Hi all,
> I just wanted to share a couple of things I've found out lately. I
> imagine they are well known to the experts here, but I thought maybe
> there are other newbies out there that could benefit from it too.
> 
> 1) Using proc in the case statement:
> 
> I find the case statement particularly elegant: especially when
> there's a long list of choices I much prefer it to using if...
> elsif... else... end. That said the latter offers a lot more
> flexibility. Still a lot can be accomplished by using procs. For
> example:
> 
> case val
> when Hash
> ...
> when lambda{|x| x.respond_to?(:to_ary) && x.length>1}
> ...
> end
> 
> The block takes the case argument and its output (generally true or
> false...) is used to decide if the branch should be run or not.
> 
> 2) Passing a block to map or similar methods.
> 
> Say you have an array of numbers, and you want to invoke #abs for each
> number. Rather than:
> x = [1,-2,3,-4,5]
> x.map{|x| x.abs}
> 
> you can use:
> x = [1,-2,3,-4,5]
> x.map(&:abs)
> 
> It may not seem much in this instance, but I found it a lot cleaner in
> some cases, especially when there is a long chain of methods.
> 
> Hope that helped _someone_ :)
> 
> Diego