From: Ruby Freak <twscannell@...>
Date: 2008-05-02T01:20:06+09:00
Subject: Please explain nuances of ||=

I am reading some of the ruby files in rails and I an seeing the ||=
method used a lot.
knowing ruby the way I do, I realize that she has lots of magical
surprises and I really want to get to know this girl!

Consider the initialize method of resources.rb

51 	      def initialize(entities, options)
52 	        @plural ||= entities
53 	        @singular ||= options[:singular] ||
plural.to_s.singularize
54 	        @path_segment = options.delete(:as) || @plural
55
56 	        @options = options
57
58 	        arrange_actions
59 	        add_default_actions
60 	        set_prefixes
61 	      end

(OK, so one iddy bitty part of this is a rails question, and dangit,
this is a ruby forum, but you guys are smarter and have better
haircuts)

Question (1)
After several hours of searching I find virtually nothing that fully
explains the line
@singular ||= options[:singular] || plural.to_s.singularize

I think know what is does, It assigns @singular a value for a
"singular named" controller if the options hash contains the
symbol :singular. I am looking more for a full description of how ||=
and  it's friends like &&= actually work.

my current understanding shows me:
 @singular = (options[:singular]) or (plural.to_s.singularize)

but the full logic seems to be more like:
if options contains a symbol named :singular then
    @singular = plural.to_s.singularize
end if

But what is the value of @singular if there is no :singular symbol?
nil?

What I think is going on is a lot more like an IF statement than a OR
statement.

Question (2)
in the line: @plural ||= entities
if entities is (false?, nil? something that fails "OR") what happens
to @plural?

Once again, the ||= seems more like an "equals If" statement rather
than an "equals Or" statement.

Question (3)
@path_segment = options.delete(:as) || @plural
 So @path_segment is assigned either the return from the delete
operation (:as) ? or the plural name of the controller. Is that
correct? Where in a common resourceful routes mapping is there an :as?

Thanks in advance for any help.