Attr_reader, etc for class variables

ruby-talk
1

Is there such a thing?

If I have the following code:
class Klass
   @@var = 0
end

How can I make an attr_writer for it besides doing
class Klass
   def var=(other)
     @@var = other
   end
end

I've tried all of these to no avail:
attr_writer :'Klass.var' # => `attr_writer': invalid attribute name `Klass.var' (NameError)

attr_writer :'var' # => undefined method `currentRound=' for Team:Class (NoMethodError) (when I try to use the writer function later)

attr_writer :'self.class.var' # => `attr_writer': invalid attribute name `self.class.var' (NameError)

Any ideas? I mean it's not a huge deal but I would like to find a way around making the method described above.

Thanks,
Dan

2

Is there such a thing?

No.

If I have the following code:
class Klass
  @@var = 0
end

How can I make an attr_writer for it besides doing
class Klass
  def var=(other)
    @@var = other
  end
end

I tend to use instance variables for this as class variables usually give me hard-to-find bugs.

class Klass
   @var = 0

   class << self
     attr_accessor :var
   end

   def some_method
     self.class.var
   end
end

p Klass.var # => 0
p Klass.new.some_method # => 0

···

On Dec 9, 2006, at 21:25 , Daniel Finnie wrote:

--
Eric Hodel - drbrain@segment7.net - http://blog.segment7.net

I LIT YOUR GEM ON FIRE!

3

Daniel Finnie wrote:

Is there such a thing?

Rails' ActiveSupport provides them as cattr_* and mattr_*. For that matter, they're not that hard to write. For that matter, what Eric said.

Devin
What, me matter?

4

Hi --

Daniel Finnie wrote:

Is there such a thing?

Rails' ActiveSupport provides them as cattr_* and mattr_*. For that matter, they're not that hard to write. For that matter, what Eric said.

I'd add that if you write them (and I agree with Eric that instance
variables are much better for this; indeed, something is pretty much
always better than class variables for everything), it's best to name
them something else. "attr" names suggest an attribute of an object,
but since class variables are not uniquely associated with any one
object, they're not a good fit for recording an attribute.

David

···

On Sun, 10 Dec 2006, Devin Mullins wrote:

--
                   David A. Black | dblack@wobblini.net
Author of "Ruby for Rails" [1] | Ruby/Rails training & consultancy [3]
DABlog (DAB's Weblog) [2] | Co-director, Ruby Central, Inc. [4]
[1] Ruby for Rails | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com | [4] http://www.rubycentral.org