Instance_eval problem

Ruby
1

Hi,

I’ ve got problem with instance_eval.

I tried the following with irb:

obj = “3”
=> “3”

obj.instance_eval “def a ; puts ‘x’; end”
=> nil

obj.a
x
=> nil

obj = 3
=> 3

obj.instance_eval “def a ; puts ‘x’; end”
TypeError: (eval):1:in `irb_binding’: no class/module to add method
from (irb):31

Why does the instance_eval not work for the Fixnum?

Best regards,
Thomas

2

Alle Wednesday 20 February 2008, bitmox ha scritto:

obj.instance_eval “def a ; puts ‘x’; end”

TypeError: (eval):1:in `irb_binding’: no class/module to add method
from (irb):31

Why does the instance_eval not work for the Fixnum?

Best regards,
Thomas

instance_eval works for Fixnums. For example:

(-1).instance_eval(“abs”)
=> 1

The problem is that you can’t define singleton methods for Fixnums (this
is
also true for Floats and Bignums):

x = 1
def x.a
end
=> TypeError: can’t define singleton method “a” for Fixnum

Stefano

3

On 20 Feb., 13:43, Stefano C. [email protected] wrote:

Best regards,
Thomas

Hi Stefano,

thank you for your hint.
I checked the documentation for Fixnum meanwhile. There is described,
that is impossible to a singleton method.

Thomas