Asp Forum - Including a class.

Ola Bini

8/29/2006 8:02:00 AM

Hi,

As an extension on my earlier question of partial includes; I just
noticed that you can't include a Class, even though it is a Module.

Anyone have a way of doing this?

What I would like to do, is to be able to dynamically mix in some good
methods from preexisting classes, depending on arguments to the
constructor. Since I need to do it dynamically, and also need it
differently for different instances of the class, I can't make it
inherit the other class.

What I would like is something like this; say I have class Foo and Bar,
with many methods in them.

class Baz < AnotherAbstractBaseClass
def initialize(config={})
self.singleton_class.module_eval do
if config[:foo]
partial_include Foo, :method1, :method7
elsif config[:bar]
partial_include Bar, :method1, :method7
end
end
end
end

Baz.new(:bar => true).method1

But I can't have an instance of Bar or Foo so delegating is impossible.
I need the methods to be in the the same instance. Any help? =)

--
Ola Bini (http://ola-bini.bl...)
JvYAML, RbYAML, JRuby and Jatha contributor
System Developer, Karolinska Institutet (http:/...)
OLogix Consulting (http://www....)

"Yields falsehood when quined" yields falsehood when quined.

3 Answers

Mauricio Fernández

8/29/2006 8:40:00 AM

On Tue, Aug 29, 2006 at 05:02:10PM +0900, Ola Bini wrote:
> As an extension on my earlier question of partial includes; I just
> noticed that you can't include a Class, even though it is a Module.
>
> Anyone have a way of doing this?
>
> What I would like to do, is to be able to dynamically mix in some good
> methods from preexisting classes, depending on arguments to the
> constructor. Since I need to do it dynamically, and also need it
> differently for different instances of the class, I can't make it
> inherit the other class.
[...]

> But I can't have an instance of Bar or Foo so delegating is impossible.
========================
> I need the methods to be in the the same instance.

Doesn't this provide a very strong indication that you want to put the
reusable methods in modules? :-)

RUBY_VERSION # => "1.8.5"
RUBY_RELEASE_DATE # => "2006-08-25"
module A; def foo; "A#foo" end end
module B; def foo; "B#foo" end end
class X; include A end
class Y; include B end
class Z
def initialize(config = {})
if config[:A]
extend A
elsif config[:B]
extend B
end
end
end

Z.new(:A => true).foo # => "A#foo"
Z.new(:B => true).foo # => "B#foo"

[See [211308] for a Module#append_from implementation that doesn't clobber
inherited methods.]

--
Mauricio Fernandez - http://eige... - singular Ruby

Ola Bini

8/29/2006 8:54:00 AM

Mauricio Fernandez wrote:
> On Tue, Aug 29, 2006 at 05:02:10PM +0900, Ola Bini wrote:
>> As an extension on my earlier question of partial includes; I just
>> noticed that you can't include a Class, even though it is a Module.
>>
>> Anyone have a way of doing this?
>>
>> What I would like to do, is to be able to dynamically mix in some good
>> methods from preexisting classes, depending on arguments to the
>> constructor. Since I need to do it dynamically, and also need it
>> differently for different instances of the class, I can't make it
>> inherit the other class.
> [...]
>
>> But I can't have an instance of Bar or Foo so delegating is impossible.
> ========================
>> I need the methods to be in the the same instance.
>
> Doesn't this provide a very strong indication that you want to put the
> reusable methods in modules? :-)
>

See, that's my problem. I have no control over them. Let me explain. I'm
working on ActiveRecord-JDBC, and sorry to say, some features of JDBC
aren't really database independent (for example, DDL). So, my current
track is to include parts of the original implementation to avoid this
problem. Right now I have copied the source verbatim, but that is no
solution. I want AR-JDBC to recognize that it's being used with an
Oracle JDBC driver, and then include some parts of OracleAdapter, (but
only parts...)

--
Ola Bini (http://ola-bini.bl...)
JvYAML, RbYAML, JRuby and Jatha contributor
System Developer, Karolinska Institutet (http:/...)
OLogix Consulting (http://www....)

"Yields falsehood when quined" yields falsehood when quined.

e

8/29/2006 2:44:00 PM

Ola Bini wrote:
> Mauricio Fernandez wrote:
>>> inherit the other class.
>> [...]
>>
>>> But I can't have an instance of Bar or Foo so delegating is impossible.
>> ========================
>>> I need the methods to be in the the same instance.
>>
>> Doesn't this provide a very strong indication that you want to put the
>> reusable methods in modules? :-)
>>
>
> See, that's my problem. I have no control over them. Let me explain. I'm
> working on ActiveRecord-JDBC, and sorry to say, some features of JDBC
> aren't really database independent (for example, DDL). So, my current
> track is to include parts of the original implementation to avoid this
> problem. Right now I have copied the source verbatim, but that is no
> solution. I want AR-JDBC to recognize that it's being used with an
> Oracle JDBC driver, and then include some parts of OracleAdapter, (but
> only parts...)

Will simple composition and delegation work?

> --
> Ola Bini (http://ola-bini.bl...)

--
Posted via http://www.ruby-....

comp.lang.ruby

Including a class.

Ola Bini

Mauricio Fernández

Ola Bini

e

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