Class eval does not work with self

Ruby
1

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 methodclass_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.

2

No, self is not Xclass inside of add_method. It’s the instance of
Xclass. If
you made add_method a class method (def self.add_method…), then it
should
work as written.

3

On Mon, Oct 25, 2010 at 4:03 PM, Andy F. [email protected]
wrote:

end

(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.

4

On 10/25/2010 10:05 AM, Jes