How to use a class_variable into a Module

ruby-talk
1

Hi, I want to declare a class_variable in class A.
Class A includes a Module M and I want some methods in M using the
class_variable but I get some problem:

···

-------------------
module M
       def kk
               #puts (eval %{ #{send('class').class_variables[0]} })
               puts @@class_var
       end
end

class A
       include M
       @@class_var = "kaka1"
end

a = A.new
a.kk
NameError: uninitialized class variable @@class_var in M
       from ./class_attr1.rb:4:in `kk'
-------------------

I understand the problem. Because the nature of class variables when
the Module M uses @@ it looks into a class variable defined in same
class/module.

Is there any way I could use a class A @class_var into a included M
module methods? If not then I'll use a normal attribute but I don't
like it since it's a constant value that could perfectly be a class
variable instead of initialiting it in each A instance creation.

Thanks a lot.

--
Iñaki Baz Castillo
<ibc@aliax.net>

2

Hi,

Iñaki Baz Castillo wrote:

Hi, I want to declare a class_variable in class A.
Class A includes a Module M and I want some methods in M using the
class_variable but I get some problem:

-------------------
module M
       def kk
               #puts (eval %{ #{send('class').class_variables[0]} })
               puts @@class_var
       end
end

class A
       include M
       @@class_var = "kaka1"
end

a = A.new
a.kk
NameError: uninitialized class variable @@class_var in M
       from ./class_attr1.rb:4:in `kk'
-------------------

I understand the problem. Because the nature of class variables when
the Module M uses @@ it looks into a class variable defined in same
class/module.

Is there any way I could use a class A @class_var into a included M
module methods? If not then I'll use a normal attribute but I don't
like it since it's a constant value that could perfectly be a class
variable instead of initialiting it in each A instance creation.

Here is a working code:

module M
      @@class_var = nil
      def kk
              puts @@class_var
      end
end

class A
      include M
      @@class_var = "kaka1"
end

a = A.new
a.kk

Regards,

Park Heesob

···

--
Posted via http://www.ruby-forum.com/\.

3

It's great!
Thanks a lot.

···

2008/5/19, Heesob Park <phasis@gmail.com>:

Here is a working code:

module M
      @@class_var = nil
      def kk

              puts @@class_var
      end
end

class A
      include M
      @@class_var = "kaka1"
end

a = A.new
a.kk

--
Iñaki Baz Castillo
<ibc@aliax.net>

4

Hi, sorry but that is not valid (at least in my case). If you include
M module in more clases, each one with its own @@class_var, then
@@class_var will be shared between them that it's not the expected
behaviour:

···

2008/5/19, Heesob Park <phasis@gmail.com>:

Here is a working code:

module M
      @@class_var = nil
      def kk

              puts @@class_var
      end
end

class A
      include M
      @@class_var = "kaka1"
end

------------------------------
module M
  @@class_var = nil
  
  def kk
    puts @@class_var
  end
end

class A
  include M
  @@class_var = "@@ A"
end

class B
  include M
  @@class_var = "@@ B"
end
------------------------------

a=A.new
a.kk
=> @@ B
(it's should be "@@ A" )

--
Iñaki Baz Castillo
<ibc@aliax.net>