From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2011-08-26T00:23:32+09:00
Subject: Re: New to Ruby some problems

On Thu, Aug 25, 2011 at 4:57 PM, jack jones <shehio_22@hotmail.com> wrote:
> thank you all very much :)

I just wanted to point out something that I think hasn't been
mentioned. In the "assignment-like" methods, where Ruby applies
syntactic sugar so that you can use the usual syntax, Ruby also does
something that is not the same as with other method calls: the result
of the "assignment" expression is the expression's right hand side,
not the result value of the method:

ruby-1.8.7-p334 :001 > class A
ruby-1.8.7-p334 :002?>   def []= a,b
ruby-1.8.7-p334 :003?>     @value = a + b
ruby-1.8.7-p334 :004?>     @value
ruby-1.8.7-p334 :005?>     end
ruby-1.8.7-p334 :006?>   end
 => nil
ruby-1.8.7-p334 :007 > a = A.new
 => #<A:0xb70bd4cc>
ruby-1.8.7-p334 :008 > a[3] = 4
 => 4
ruby-1.8.7-p334 :009 > a
 => #<A:0xb70bd4cc @value=7>

Note that the value of the expression in line 8 is 4 (as shown by IRB)
and not 7, which is the value returned by the method []=
If you use the non-syntactic sugar version, though, the return value
is whatever the method returns:


ruby-1.8.7-p334 :010 > a.[]=(3,4)
 => 7

This is usually not a problem, since for this to bite you, you need to
be doing something in the []= and trying to use that return value
outside, not very likely. But anyway, I thought it was worth
mentioning.

Jesus.