From: Brian Candler <b.candler@...>
Date: 2008-11-26T21:17:08+09:00
Subject: Re: attr_reader, default attribute value, and rdoc of attrib

dkmd_nielsen wrote:
> What I want to do is create an attribute, allow it to have a default
> value, and have the attribute documented as such (and not as a method)
> with rdoc.  So, would the proper syntax for accomplishing this
> elementary feat be:
> 
>    # Field (row) delimiter.  Default is a comma.
>    attr_reader fld_delimiter
> 
>    # :call-seq:
>     #   fld_delimiter
>     #
>     # Returns the field (column) delimiter.  Default is comma.
>     def fld_delimiter #:nodoc:
>       !@fld_delimiter.nil? ? @fld_delimiter : (@fld_delimiter = ',')
>     end
> 
>     # :call-seq:
>     #   fld_delimiter(String)
>     #
>     # Assign a field (column) delimiter.
>     def fld_delimiter=(d)
>       @fld_delimiter = d
>     end

I would tidy this up as:

attr_accessor :fld_delimiter
def fld_delimiter #:nodoc:
  @fld_delimiter ||= ','
end

That assumes you never want to assign nil or false as a fld_delimiter. 
If you do, then

attr_accessor :fld_delimiter
def fld_delimiter #:nodoc
  @fld_delimiter = ',' unless defined? @fld_delimiter
  @fld_delimiter
end

Another option is never to assign when defaults are being used: using a 
constant lets you document the default.

DEFAULT_FLD_DELIMITER = ','.freeze
attr_accessor :fld_delimiter
def fld_delimiter
  defined? @fld_delimiter ? @fld_delimiter : DEFAULT_FLD_DELIMITER
end

However I think it would be simpler just to set @fld_delimiter=',' in 
your object's initialize method.
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