From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2010-10-26T00:05:59+09:00
Subject: Re: Class eval does not work with self

On Mon, Oct 25, 2010 at 4:03 PM, Andy Frank <ridingwithrails@gmail.com> wrote:
> I am experimenting with a test class to figure out why self.class_eval
> does not seem to work.  Please see code below:
>
>  class Xclass
>         def add_method(meth, work)
>          self.class_eval %Q{
>                 def #{meth}
>                         #{work}
>                 end
>                 }
>         end
> end
>
> This throws an error when I call the class like so:
>
> x = Xclass.new
> x.add_method("add", "puts \"Hello World\"")
>
>
> Error:
> rb:3:in `add_method': undefined method `class_eval' for #
> (NoMethodError)
>  from test_dyn.rb:15:in `'
>
>
> The fix has been to change self.class_eval  to Xclass.class_eval.
> Anyone know why this is the case. Shouldn't self work.

You can also use self.class.class_eval:

irb(main):001:0> class Xclass
irb(main):002:1> def add_method(meth,work)
irb(main):003:2> self.class.class_eval %Q{
irb(main):004:2" def #{meth}
irb(main):005:2" #{work}
irb(main):006:2" end
irb(main):007:2" }
irb(main):008:2> end
irb(main):009:1> end
=> nil
irb(main):010:0> x = Xclass.new
=> #<Xclass:0xb74f77b8>
irb(main):011:0> x.add_method("add", 'puts "hello world"')
=> nil
irb(main):012:0> x.add
hello world

Jesus.