Changing self in Ruby

How many ways are there to change self in Ruby? I count (excluding thread switching):

• method invocation
• class and module definition
• instance_ and class/module_eval
• invocation of a proc

What am I missing?

Comments

[ko1]

require/load change scope/self.

[Chris Bernard]

The value of self does change in a method definition, in which it's nil. This scenario could be considered distinct from "class and module definition".

[Dave Thomas]

Chris:

I'm intrigued: how is it possible to tell from the Ruby level what the value of self is during a method definition?

[Dave Thomas]

ko1:

I believe self is unchanged by require, but the scoping is changed so that local variables aren't accessible. If you set an instance variable in a required file, though, it is accessible after the require.

Dave

[JEG2]

I'm not getting how self changes with the invocation of a Proc. Scope definitely changes, but self? It seems like the same kind of change as require/load.

[ko1]

I meant that:

----------------------------
# a.rb
class C
p self #=> C
require 'b'
end

----------------------------
# b.rb
p self #=> main
----------------------------

The reason why I posted this comment is I implemented it on YARV :)

[Chris Bernard]

Dave:

Well, I was wrong. While playing around I had written this:

$cself; $mself
class C
$cself = self
def meth; $mself = self; end
end
p $cself # => C
p $mself # => nil

... so I mistakenly thought that self was nil while in a method definition.

But it turns out of course that the assignment to the global $mself within the method definition does not happen at all. The value of $mself is only nil because that's its initial value.

[Ken Bloom]

JEG2: What he means is this:

class B
def foo
p self
yield
end
def inspect
"a B object"
end
end

B.new.foo { p self }

When run, this gives:
a B object
main

[JEG2]

I see now. Makes sense.