From: Joel VanderWerf <vjoel@...>
Date: 2006-10-26T13:50:16+09:00
Subject: Re: Pass block instead of here document?

Rick DeNatale wrote:
...
> But in Smalltalk if you write:
> 
>   obj msg1;msg2
> 
> the object referenced by obj is sent msg1 and then msg2 in sequence,
> regardless of the value returned by obj msg1.

Not quite the same, but this is something similar that's been floating 
around the ml for a while:

class Object
   def then
     yield(self)
     self
   end
end

hash = Hash.new.
  then do |h| h[1] = 2 end.
  then do |h| h[3] = 4 end

p hash

That's much clunkier syntactically, but it is actually useful in one 
case: when working with classes whose #new method doesn't take a block 
that allows further configuration of the new object. For example, sockets:

def socket
   @socket ||= UDPSocket.open.then do |s|
     s.setsockopt(Socket::SOL_SOCKET, Socket::SO_BROADCAST, true)
     s.connect("192.168.255.255", 1234)
   end
end

It works particularly well with the ||= assignment operator.

Without the #then method you can't use ||= and it's just a little clunkier:

def socket
   unless @socket
     @socket = UDPSocket.open
     @socket.setsockopt(Socket::SOL_SOCKET, Socket::SO_BROADCAST, true)
     @socket.connect("255.255.255.255", 1234)
   end
   @socket
end

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407