Are methods objects?

[Marc Heiler]

Before someone showed me
methodputs).class
I thought methods are no objects.

But class Method seems to exist, with
Method.class giving back Class,
so
Method.class.new
would be the same as
Class.new

I guess one can extend every Class.new via
instance_eval, but my problem here fundamentally is,
why is a method an object? And if I can create a
new object from any method...

What I now see is that every object in ruby has methods,
which are objects as well. Did I make a mistake? Are methods
no objects? Or why are methods objects too?

 

[David A. Black]

Hi --

Before someone showed me
methodputs).class
I thought methods are no objects.

But class Method seems to exist, with
Method.class giving back Class,
so
Method.class.new
would be the same as
Class.new

I guess one can extend every Class.new via
.instance_eval, but my problem here fundamentally is,
why is a method an object? And if I can create a
new object from any method...

What I now see is that every object in ruby has methods,
which are objects as well. Did I make a mistake? Are methods
no objects? Or why are methods objects too?

Methods can be objectified, so to speak. Each Method object is a kind
of wrapper around a method. The methods themselves are not first-class
objects.

You can see the wrapper effect by comparing object ids:
=> 1310220

There's no Method.new; you have to get a Method object via an object.
You can unbind a method from a given object and bind it to another
(within certain rules, mainly having to do with class):
=> ["d", "e", "f"]

Another point I'd make is that objects don't really have methods.
Classes and modules contain method definitions; objects have the
intelligence to go looking for method definitions, along a
predetermined class/module path, when they receive messages. I know
that sounds like a wordy way to put it (and there's nothing wrong with
saying that an object "has" methods, informally), but it becomes
important when you get deeply into the way classes and modules and
message resolution work.


David

--
David A. Black / Ruby Power and Light, LLC
Ruby/Rails consulting & training: http://www.rubypal.com
Now available: The Well-Grounded Rubyist (http://manning.com/black2)
"Ruby 1.9: What You Need To Know" Envycasts with David A. Black
http://www.envycasts.com

 

[Robert Klemme]

Before someone showed me
methodputs).class
I thought methods are no objects.

But class Method seems to exist, with
Method.class giving back Class,
so
Method.class.new
would be the same as
Class.new

I guess one can extend every Class.new via
instance_eval, but my problem here fundamentally is,
why is a method an object? And if I can create a
new object from any method...

You can't just create a new object from any method. "Method.class.new"
works for all other classes as well because, as you have clearly seen,
"Method.class" returns "Class". "Class.new" in turn creates a new
object - but it's a class object! To get an instance you would have to
do "Class.new.new".

For the other questions please see David's excellent explanation.

Kind regards

robert

 

[Marc Heiler]

For the other questions please see David's excellent explanation.

Yes but right now my world seems heavily ... changed.
These two lines caused that:

1) "abc".methodsplit).unbind.bind("def").call(//) => ["d", "e", "f"]

and

2) Another point I'd make is that objects don't really have methods.

I am still in shock. I haven't seen that sneaky bastard UnboundMethod
before either ...