From: Stefan Lang <langstefan@...>
Date: 2005-07-29T07:30:04+09:00
Subject: Re: self.x=(value) in private?

On Friday 29 July 2005 00:24, Stefan Lang wrote:
> On Thursday 28 July 2005 23:59, Mark Volkmann wrote:
[...]
> > An expression that looks like '@attr-name = value' always calls a
> > method whose name is 'attr-name='.
>
> No it's the other way round. Most methods looking like 'attr_name='
> are implemented like this:
>
>     # public accessor method
>     def attr_name=(val)
>         # Set instance variable @attr_name
>         # @attr_name is only accessible in methods of self
>         @attr_name = val
>     end
>
> Let's look at an example:
>
>     % cat foo.rb
>     class Foo
>         def initialize
>            @text = ""
>         end
>         def text=(val)
>             # an empty string is a "true value" in Ruby,
>             # nil is a "false value"
>             @text = val || ""
>         end
>         def text
>             # just return @text
>             @text
>         end
>         def set_nil
>             @text = nil
              # replace the above line with:
              #   self.text = nil
              # and the method text= we've defined above will
              # be called
>         end
>     end
>
>     a = Foo.new
>     a.text = nil
>     b = Foo.new
>     b.set_nil
>     p a.text
>     p b.text
>     % ruby foo.rb
>     ""
>     nil

HTH,
  Stefan