Re: Changing self class from inside a method??

The class-oriented idiom is very strict. I.e An object is an instance of a c=
lass.

However, leaving classes behind, objects are nothing but state and behavior.=


In ruby and other purely object oriented languages, an object isn't judged o=
n it's class but on it's behavior (ducktyping).

Thus you don't need to change the class of an object ---which isn't much mor=
e than a factory to create object --- to achieve what you want.

- Mixins allows you to inject behavior to objects at runtime.
- It's possible to alter (undef) methods
- You might want to github search for Mixology
- Read about Role modeling (maybe DCI) and traits.

On May 22, 2012, at 9:03 AM, Robert Klemme <[e-mail]> wrot=
e:

> On Tue, May 22, 2012 at 6:43 AM, David Madison <[e-mail]> wrot=
e:
>> Let's start off with the assumption I want a method that allows an
>> object to transform itself into another object.  In other words:
>>=20
>>=20
>> begClass =3D a.class
>> a.changeToSomethingElse(42)
>> endClass =3D a.class
>>=20
>> # Where begClass !=3D endClass
>=20
> You can't do this.
>=20
>> As a more specific example, consider some hopeful code for allowing
>> auto-creation of arrays from nil, perl-ish style:
>=20
> If you miss Perl that much you are probably using the wrong language here.=

>=20
>> class Nil
>>  def push(*els)
>>    a =3D Array.new
>>    a.push(*els)
>>    #self =3D a             # Nope!
>>    #self.class =3D Array   # Nope!
>>  end
>> end
>>=20
>> This would allow:
>>  a =3D nil
>>  a.push(1,2,3)
>>  puts "#{a.class}"
>>=20
>> I know we have things like to_a, but that requires an assigment instead
>> of just the method call.  Let's just assume we need a way to do it like
>> this.
>=20
> I am not ready to assume "that we need a way to do it like this".  The
> Ruby idiom for this is
>=20
> a =3D nil
> ...
> (a ||=3D[]).push(1,2,3)
>=20
>> Is this just considered impossible, or is there a way to change/convert
>> the class of self from inside a method?  I can imagine it would cause
>> complications the moment the class changes, since we'd suddenly be in
>> the method of the wrong class, but if any language had a way to do it, I
>> figure it'd be ruby.
>=20
> There might be a way in a C extension but actually I consider it a bad
> idea because it violates one of the basic assumptions of the language
> (i.e. that the class of an instance does not change) - and it's
> unnecessary (see above).
>=20
> What you can do is to use a proxy object like SimpleDelegator and
> change the instance it points to later.  But then you need to
> initialize the variable and if you know it's going to be an Array you
> can just as well initialize with an empty Array instance.
>=20
> Kind regards
>=20
> robert
>=20
> --=20
> remember.guy do |as, often| as.you_can - without end
> http://blog.rubybestpractices.com/
>=20