Is it the same context when a class is the receiver of instance_eval or
class_eval/module_eval?
On 8/10/06, Andrew G. [email protected] wrote:
Is it the same context when a class is the receiver of instance_eval or
class_eval/module_eval?
No. In case of instance_eval you will be in the class, and in the
case of (class|module)_eval you will be in the class of the class
(which is Class) [Hurray for multiple meanings to a word!]
“A” == Arnaud B. [email protected] writes:
A> No. In case of instance_eval you will be in the class, and in the
A> case of (class|module)_eval you will be in the class of the class
A> (which is Class) [Hurray for multiple meanings to a word!]
no, not really. ruby use self and internally ruby_class which give it
where it can define method when it find keyword like ‘def’, ‘alias’,
…
With obj.instance_eval ruby will make
- self = obj , ruby_class = obj singleton class
This mean that inside instance_eval it will define singleton method
#instance_eval work with any object, but a class is a little special
because it can be seen as an object or as a class. This is why
#module_eval, #class_eval exist.
With obj.class_eval ruby will make
- self = obj, ruby_class = obj
This mean that inside class_eval ruby will define instance method.
One way to see it
moulon% ruby -e ‘class A; end; A.instance_eval{ p self; def a() puts
“A::a” end}; A.a’
A
A::a
moulon%
moulon% ruby -e ‘class A; end; A.class_eval{ p self; def a() puts “A#a”
end}; A.new.a’
A
A#a
moulon%
Guy Decoux
On Aug 11, 2006, at 11:14 AM, ts wrote:
With obj.instance_eval ruby will make
- self = obj, ruby_class = obj
moulon% ruby -e ‘class A; end; A.class_eval{ p self; def a() puts
“A#a” end}; A.new.a’
A
A#a
moulon%
I’ve always had trouble understanding this and for some reason this
is the email that finally clicked all the pieces into place for me.
Thanks Guy!
James Edward G. II