'<<' operator

Ruby
1

I have a small doubt on wht the ‘<<’ operator do in ruby

for instance in this code

class << ro
undef :instance_eval
end

2

Hi,

This has nothing to do with the << operator. It’s the syntax of the
eigenclass of ro.

3

Ok thanks for the reply Jan,
Can u please ellaborate on the eigenclass and wht is it used for.

4

The eigenclass contains all singleton methods of an object. Those are
methods which don’t come from the class of the object but actually
belong to the object itself.

For example:

class A
def f
puts 1
end
end

a_1, a_2 =
A.new, A.new

define a singleton method for a_1

def a_1.g
puts 2
end

call instance method f (defined in class A)

a_1.f
a_2.f

call singleton method g (defined in singleton class of a_1)

a_1.g
a_2.g # this doesn’t work, because a_2 doesn’t have the method

Instead of writing def a_1.g, you could also explicitly define the
method in the eigenclass of a_1:

class << a_1
def g
puts 2
end
end