From: "Peña, Botp" <botp@...>
Date: 2007-09-01T12:42:50+09:00
Subject: Re: attr_reader

From: 7stud 7stud [mailto:dolgun@excite.com] 
# "The corresponding instance variables, @name, @artist, and @duration,
# will be created for you."

that should read: "The corresponding instance variable getter and setter methods will be created for you."
 
irb(main):092:0> system "qri instance_variables"
---------------------------------------------- Object#instance_variables
     obj.instance_variables    => array
------------------------------------------------------------------------
     Returns an array of instance variable names for the receiver. Note
     that simply defining an accessor does not create the corresponding
     instance variable.

        class Fred
          attr_accessor :a1
          def initialize
            @iv = 3
          end
        end
        Fred.new.instance_variables   #=> ["@iv"]


#So, it seems like initialize is what creates the instance variables.

not really. 

irb(main):097:0> class Song2
irb(main):098:1>   attr_accessor :x, :y
irb(main):099:1> end
=> nil

note, no initialization there

irb(main):106:0> ix=Song2.new
=> #<Song2:0xb7d7efa8>
irb(main):107:0> ix.instance_variables
=> []
irb(main):108:0> ix.x="hi, i am x"
=> "hi, i am x"

note the assignment using the setter method automatically created using attr_accessor

irb(main):109:0> ix.x
=> "hi, i am x"

now, we've created an instance var

irb(main):110:0> ix.instance_variables
=> ["@x"]
irb(main):111:0>

kind regards -botp