[#395238] rubygem: ispunity (unite all your internet connections) — Arun Tomar <tomar.arun@...>

Dear friends,

12 messages 2012/05/01

[#395250] Overwriting one Ruby array or arrays with another — Craig Law <lists@...>

Hi

14 messages 2012/05/02

[#395258] array of strings - finding letter combinations — "Sebastjan H." <lists@...>

Hi All,

16 messages 2012/05/02

[#395357] Why Enumerator#next does not return more than one value? — Földes László <lists@...>

If I have an Enumerator which yields elements of a mathematical series

10 messages 2012/05/07

[#395373] How to use Data_Wrap_Struct to assign the DATA VALUE to an exsiting Ruby object? — Iñaki Baz Castillo <ibc@...>

Hi, my code receives an arbitrary klass name (provided by the user)

8 messages 2012/05/07

[#395429] passing via instance variable or regular () — sam jam <lists@...>

def first

10 messages 2012/05/10

[#395463] I'm looking for a Metaprogramming Project — Phil Stone <lists@...>

Hello,

19 messages 2012/05/11

[#395548] A million reasons why Encoding was a mistake — Marc Heiler <lists@...>

Newcomer wants to try Ruby.

15 messages 2012/05/15
[#395561] Re: A million reasons why Encoding was a mistake — Ryan Davis <ryand-ruby@...> 2012/05/15

[#395595] Re: A million reasons why Encoding was a mistake — Brian Candler <lists@...> 2012/05/16

I will add that the OP is not entirely alone in his opinion.

[#395551] How to ensure that a block runs entirely after other threads? (Thread.exclusive does not "work") — Iñaki Baz Castillo <ibc@...>

Hi, I expected that in the following example code, thread t1 would not

8 messages 2012/05/15

[#395575] GUI with ruby on windows — David Acosta <lists@...>

hello friends, i am a begginer and i have a litlle question, how can i

17 messages 2012/05/16

[#395604] what is going wrong here? — roob noob <lists@...>

Notice the initialization of both classes in each of the examples, if

20 messages 2012/05/16

[#395646] rb_gc_register_address() or rb_gc_mark()? — Iñaki Baz Castillo <ibc@...>

Hi, I've bad experiences with rb_gc_register_address(), it does never

16 messages 2012/05/17

[#395686] reading from and writing to a Unicode encoded file — "Sebastjan H." <lists@...>

Hi,

19 messages 2012/05/18
[#395694] Re: reading from and writing to a Unicode encoded file — Regis d'Aubarede <lists@...> 2012/05/18

Hello,

[#395697] Re: reading from and writing to a Unicode encoded file — "Sebastjan H." <lists@...> 2012/05/18

Regis d'Aubarede wrote in post #1061272:

[#395698] Re: reading from and writing to a Unicode encoded file — Regis d'Aubarede <lists@...> 2012/05/18

Sebastjan H. wrote in post #1061276:

[#395699] Re: reading from and writing to a Unicode encoded file — "Sebastjan H." <lists@...> 2012/05/18

Regis d'Aubarede wrote in post #1061277:

[#395750] Re: reading from and writing to a Unicode encoded file - issues when using Shoes — "Sebastjan H." <lists@...> 2012/05/21

Hi,

[#395754] Re: reading from and writing to a Unicode encoded file - issues when using Shoes — "Sebastjan H." <lists@...> 2012/05/21

Sebastjan H. wrote in post #1061483:

[#395740] ? Ruby through CGI and Rails — Shaun Lloyd <list@...>

Hi everybody,

22 messages 2012/05/21
[#395764] Re: Ruby through CGI and Rails — Brian Candler <lists@...> 2012/05/21

Shaun Lloyd wrote in post #1061455:

[#395786] Re: Ruby through CGI and Rails — Shaun Lloyd <list@...> 2012/05/22

On 22/05/12 03:37, Brian Candler wrote:

[#395838] Re: Ruby through CGI and Rails — Brian Candler <lists@...> 2012/05/23

Shaun Lloyd wrote in post #1061602:

[#395787] Changing self class from inside a method?? — David Madison <lists@...>

Let's start off with the assumption I want a method that allows an

10 messages 2012/05/22

[#395841] Memory-efficient set of Fixnums — George Dupre <lists@...>

Hi,

25 messages 2012/05/23

[#395883] looking for a ruby idiom : r=foo; return r if r — botp <botpena@...>

Hi All,

11 messages 2012/05/24

[#395966] Am I justified to use a global variable if it must be used in all scopes? — Phil Stone <lists@...>

Hello,

12 messages 2012/05/27

[#396010] does this leak more than the size of the string via timing side channels — rooby shoez <lists@...>

string1 = "string"

16 messages 2012/05/29

[#396038] Is it possible to avoid longjmp in exceptions, Thread#kill, exit(), signals? — Iñaki Baz Castillo <ibc@...>

Hi, my Ruby C extension runs a C loop (libuv) without GVL. At some

8 messages 2012/05/29

Re: Changing self class from inside a method??

From: Robert Klemme <shortcutter@...>
Date: 2012-05-22 07:03:24 UTC
List: ruby-talk #395790
On Tue, May 22, 2012 at 6:43 AM, David Madison <lists@ruby-forum.com> wrote=
:
> Let's start off with the assumption I want a method that allows an
> object to transform itself into another object. =A0In other words:
>
>
> begClass =3D a.class
> a.changeToSomethingElse(42)
> endClass =3D a.class
>
> # Where begClass !=3D endClass

You can't do this.

> As a more specific example, consider some hopeful code for allowing
> auto-creation of arrays from nil, perl-ish style:

If you miss Perl that much you are probably using the wrong language here.

> class Nil
> =A0def push(*els)
> =A0 =A0a =3D Array.new
> =A0 =A0a.push(*els)
> =A0 =A0#self =3D a =A0 =A0 =A0 =A0 =A0 =A0 # Nope!
> =A0 =A0#self.class =3D Array =A0 # Nope!
> =A0end
> end
>
> This would allow:
> =A0a =3D nil
> =A0a.push(1,2,3)
> =A0puts "#{a.class}"
>
> I know we have things like to_a, but that requires an assigment instead
> of just the method call. =A0Let's just assume we need a way to do it like
> this.

I am not ready to assume "that we need a way to do it like this".  The
Ruby idiom for this is

a =3D nil
...
(a ||=3D[]).push(1,2,3)

> Is this just considered impossible, or is there a way to change/convert
> the class of self from inside a method? =A0I 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.

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).

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.

Kind regards

robert

--=20
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

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