Is it the same context when a class is the receiver of instance_eval or
class_eval/module_eval?
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Posted via http://www.ruby-forum.com/.
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!]
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On 8/10/06, Andrew Gibson <gibson_andrew@yahoo.com> wrote:
Posted via http://www.ruby-forum.com/\.
--
"What is your function in life?" - Killer
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!]
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
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
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A::a
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 Gray II
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On Aug 11, 2006, at 11:14 AM, ts wrote:
> 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!]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 classThis 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%