dynamic include

[Florian Aßmann]

Hello,

I try to include some modules to a class instance, but I have
problems with the scope, here's what I did:


person.roles.each do |role|
class << person
include role.class.const_get('Functions')
end if role.class.const_defined?('Functions')
end unless person.nil?


As you can see role is not defined when I include it, does anybody
know how I can add some singleton methods to person?

Regards
Florian

 

[David Vallner]

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As you can see role is not defined when I include it, does anybody know=

how I can add some singleton methods to person?
=20

Maybe the module Functions is the culprit? Are the methods module
functions ("def self.some_method"), or mixin functions ("def
some_method") in the module?

David Vallner


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[Florian Aßmann]

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Am 01.10.2006 um 20:53 schrieb David Vallner:

Maybe the module Functions is the culprit? Are the methods module
functions ("def self.some_method"), or mixin functions ("def
some_method") in the module?

David Vallner

Mixin:

class ManagerRole < Role
module Functions
def hire( person )
self.company << person
end
end
end

Florian
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[Florian Aßmann]

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Am 01.10.2006 um 20:53 schrieb David Vallner:

Maybe the module Functions is the culprit? Are the methods module
functions ("def self.some_method"), or mixin functions ("def
some_method") in the module?

David Vallner

To be complete here if the Exception:

NameError: undefined local variable or method `role' for =20
#<Class:#<Person:0x2869aa0>>
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/=20
active_record/base.rb:1129:in `method_missing'
/Users/boof/Documents/Workspaces/rails/comany/config/../app/=20
models/person.rb:63:in `auth'
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/=20
active_record/associations/association_proxy.rb:110:in `each'
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/=20
active_record/associations/association_proxy.rb:110:in `send'
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/=20
active_record/associations/association_proxy.rb:110:in `method_missing'
/usr/local/lib/ruby/gems/1.8/gems/activerecord-1.14.4/lib/=20
active_record/associations/has_and_belongs_to_many_association.rb:=20
81:in `method_missing'
/Users/boof/Documents/Workspaces/rails/comany/config/../app/=20
models/person.rb:60:in `auth'
test/unit/person_test.rb:37:in `test_4_change_password'


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[David Vallner]

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To be complete here if the Exception:
=20
NameError: undefined local variable or method `role' for
#<Class:#<Person:0x2869aa0>>

I smell a Ruby bug / gotcha.

Apparently, in metaclass scope, the surrounding scope just isn't visible.=


Try a workaround:

person.roles.each do |role|
if role.class.const_defined?('Functions')
class << person
self
end.class_eval do
include role.class.const_get('Functions')
end
end
end unless person.nil?

David Vallner

PS: Statement modifiers after whole blocks? Ick.


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[dblack]

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Hi --

I smell a Ruby bug / gotcha.

Apparently, in metaclass scope, the surrounding scope just isn't visible.

The class keyword always creates a new scope, whether you give it a
constant argument or a "<< obj"-style argument.

Try a workaround:

person.roles.each do |role|
if role.class.const_defined?('Functions')
class << person
=09 self
end.class_eval do
include role.class.const_get('Functions')
end
end
end unless person.nil?

You could also use extend, and avoid having to do the thing that won't
be easy until RCR 231 is accepted

person.roles.each do |role|
if role.class.const_defined?('Functions')
person.extend role.class.const_get('Functions')
end
end


David

--=20
David A. Black | (e-mail address removed)
Author of "Ruby for Rails" [1] | Ruby/Rails training & consultancy [3]
DABlog (DAB's Weblog) [2] | Co-director, Ruby Central, Inc. [4]
[1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com | [4] http://www.rubycentral.org
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[David Vallner]

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You could also use extend, and avoid having to do the thing that won't
be easy until RCR 231 is accepted

Could've sworn extend was private or protected... On second thought,
that would make the method pretty much useless.

*facewall*

There goes the attempt at remembering the little I can about the messier
meta stuff.

David Vallner

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[Florian Aßmann]

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Am 01.10.2006 um 21:14 schrieb David Vallner:

I smell a Ruby bug / gotcha.

Apparently, in metaclass scope, the surrounding scope just isn't =20
visible.

Try a workaround:

person.roles.each do |role|
if role.class.const_defined?('Functions')
class << person
self
end.class_eval do
include role.class.const_get('Functions')
end
end
end unless person.nil?

David Vallner

PS: Statement modifiers after whole blocks? Ick.

Ok, I just tested it, but now even a person with a CustomerRole and =20
no ManagerRole role has the methods once they are included, thanks =20
anyway.
dblack, extend works excactly the way I want it to, thank you too

Result...

if person =3D self.send( dyn_finder, *find_args )
m_name =3D 'Functions'
functions =3D person.roles.inject([]) do |f,r|
r.class.const_defined?(m_name) and
f << r.class.const_get(m_name)
end and person.extend *functions
end

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[dblack]

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Hi --

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Am 01.10.2006 um 21:14 schrieb David Vallner:


Ok, I just tested it, but now even a person with a CustomerRole and no=20
ManagerRole role has the methods once they are included, thanks anyway. := D
dblack, extend works excactly the way I want it to, thank you too

The two techniques should give you the same results. If you have a
case where they don't, I'd be interested in seeing it.

Result...

if person =3D self.send( dyn_finder, *find_args )
m_name =3D 'Functions'
functions =3D person.roles.inject([]) do |f,r|
r.class.const_defined?(m_name) and
f << r.class.const_get(m_name)
end and person.extend *functions
end

That call to inject will always return an array, so the "and" will
always flip to the right and execute person.extend *functions -- even
if functions is empty, in which case you'll get an error. You'd
probably want to drop the "and" and just do a conditional test:

person.extend *functions unless functions.empty?


David

--=20
David A. Black | (e-mail address removed)
Author of "Ruby for Rails" [1] | Ruby/Rails training & consultancy [3]
DABlog (DAB's Weblog) [2] | Co-director, Ruby Central, Inc. [4]
[1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com | [4] http://www.rubycentral.org
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[Florian Aßmann]

After a Test/Unit failed because of an Exception I did: <code>p
functions</code> in my source.
It shows me that at one time <var>functions</var> was False, so I
added the && operator.

Regards
Florian