# Pattern for "include"ing class methods?

**URL:** <https://www.ruby-forum.com/t/pattern-for-include-ing-class-methods/128247>\
**Category:** Ruby\
**Created:** [February 6, 2008, 5:00am UTC](https://www.ruby-forum.com/t/pattern-for-include-ing-class-methods/128247 "2008-02-06T05:00:55Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![Clifford\_H](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/49beb7/32.png) [@Clifford\_H](https://www.ruby-forum.com/u/Clifford_H)\
**Post date:** [February 6, 2008, 5:00am UTC](https://www.ruby-forum.com/t/pattern-for-include-ing-class-methods/128247/1 "2008-02-06T05:00:55Z")

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I’m doing some meta-programming where I want to add the same  
instance and class methods to many other existing classes,  
which I don’t wish to re-superclass.

include works nicely for including instance methods,  
but to make class extensions as well, I need to use extend  
with a module that uses class\_def (from \_why’s metaid.rb)

Is there a way to avoid having to make two separate extension  
modules and apply them separately, as in:

class Foo \< …whatever…  
include InstanceExtensions  
extend ClassExtensions  
…  
end

What I’d like is to define one extension module having both  
class and instance methods, and insert them both into my class  
with one statement. If I include and extend the same module,  
like Facet’s include\_and\_extend used to do, I get the instance  
methods defined on the classes as well as the instances.

Any thoughts?

Clifford H…

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**Author:** ![Clifford\_H](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/49beb7/32.png) [@Clifford\_H](https://www.ruby-forum.com/u/Clifford_H)\
**Post date:** [February 6, 2008, 6:05am UTC](https://www.ruby-forum.com/t/pattern-for-include-ing-class-methods/128247/2 "2008-02-06T06:05:56Z")

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On Feb 5, 2008, at 8:59 PM, Clifford H. wrote:

> methods defined on the classes as well as the instances.
> 
> Any thoughts?
> 
> Clifford H…

module M  
module ClassMethods  
end

```
module InstanceMethods
end

def M.inherited other
  other.send :extend, ClassMethods
  other.send :include InstanceMethods

```

end  
end

a @ [http://codeforpeople.com/](http://codeforpeople.com/)

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<div class="post-metadata">

**Author:** ![Clifford\_H](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/49beb7/32.png) [@Clifford\_H](https://www.ruby-forum.com/u/Clifford_H)\
**Post date:** [February 6, 2008, 6:55am UTC](https://www.ruby-forum.com/t/pattern-for-include-ing-class-methods/128247/3 "2008-02-06T06:55:48Z")

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ara howard wrote:

> end  
> end

Interesting idea, but it doesn’t seem to work, and I don’t see  
how it could (though I’ve mangled it into something different  
that does work).

How and when should module M get used, and how does inherited  
get called?

My look at the Ruby doc says the “inherited” callback only works  
on classes, not on modules…? Is this a 1.9 thing? If I change  
M to a class, then of course I can’t use it as the argument to  
include or extend :-).

What I _did_ get to work was to add a method to class Module that  
does the include and extend. Which I guess I knew I could do anyhow…

Clifford H…

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<div class="post-metadata">

**Author:** ![Clifford\_H](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/49beb7/32.png) [@Clifford\_H](https://www.ruby-forum.com/u/Clifford_H)\
**Post date:** [February 6, 2008, 5:18pm UTC](https://www.ruby-forum.com/t/pattern-for-include-ing-class-methods/128247/4 "2008-02-06T17:18:28Z")

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2008/2/6, Clifford H. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):

> > ```
> > other.send :include InstanceMethods
> > 
> > ```
> 
> My look at the Ruby doc says the “inherited” callback only works  
> on classes, not on modules…? Is this a 1.9 thing? If I change  
> M to a class, then of course I can’t use it as the argument to  
> include or extend :-).
> 
> What I _did_ get to work was to add a method to class Module that  
> does the include and extend. Which I guess I knew I could do anyhow…

What stops you from doing

module InstMeths  
end

module ClassMeths  
end

def adjust(cl)  
cl.extend ClassMeths  
cl.send :include, InstMeths  
end

adjust MyClass  
adjust YourClass

or even

set\_of\_classes.each {|cl| adjust cl}

? (probably with a more expressive method name than “adjust”)

Kind regards

robert

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<div class="post-metadata">

**Author:** ![Clifford\_H](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/49beb7/32.png) [@Clifford\_H](https://www.ruby-forum.com/u/Clifford_H)\
**Post date:** [February 6, 2008, 4:55pm UTC](https://www.ruby-forum.com/t/pattern-for-include-ing-class-methods/128247/5 "2008-02-06T16:55:18Z")

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Alle Wednesday 06 February 2008, Clifford H. ha scritto:

> > ```
> > other.send :include InstanceMethods
> > 
> > ```
> 
> My look at the Ruby doc says the “inherited” callback only works  
> on classes, not on modules…? Is this a 1.9 thing? If I change  
> M to a class, then of course I can’t use it as the argument to  
> include or extend :-).
> 
> What I _did_ get to work was to add a method to class Module that  
> does the include and extend. Which I guess I knew I could do anyhow…
> 
> Clifford H…

I think you need M.included, not M.inherited:

module M

module ClassMethods  
def m1  
puts “m1”  
end  
end

module InstanceMethods  
def m2  
puts “m2”  
end  
end

def self.included other  
other.send :include, InstanceMethods  
other.send :extend, ClassMethods  
end  
end

class C  
include M  
end

C.m1  
C.new.m2

Stefano

Stefano

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<div class="post-metadata">

**Author:** ![Clifford\_H](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/49beb7/32.png) [@Clifford\_H](https://www.ruby-forum.com/u/Clifford_H)\
**Post date:** [February 6, 2008, 10:25pm UTC](https://www.ruby-forum.com/t/pattern-for-include-ing-class-methods/128247/6 "2008-02-06T22:25:56Z")

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ara howard wrote:

> On Feb 6, 2008, at 8:54 AM, Stefano C. wrote:
> 
> > I think you need M.included, not M.inherited:  
> > yeah - typo - sorry.  
> > it definitely works - i use it everywhere…

Thanks all, exactly what I wanted, works like a charm.

Clifford H…

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<div class="post-metadata">

**Author:** ![Clifford\_H](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/49beb7/32.png) [@Clifford\_H](https://www.ruby-forum.com/u/Clifford_H)\
**Post date:** [February 6, 2008, 7:13pm UTC](https://www.ruby-forum.com/t/pattern-for-include-ing-class-methods/128247/7 "2008-02-06T19:13:25Z")

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On Feb 6, 2008, at 8:54 AM, Stefano C. wrote:

> I think you need M.included, not M.inherited:

yeah - typo - sorry.

it definitely works - i use it everywhere…

cheers.

a @ [http://codeforpeople.com/](http://codeforpeople.com/)