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From: Smart RoR on 22 Mar 2010 22:11
Hello:

Can Modules extends within themselves?

Like Class A < B is Valid, where B is another class
Module X < Y is invalid, where Y is another module?


Thanks.
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From: Robert Klemme on 23 Mar 2010 17:51
On 03/23/2010 03:11 AM, Smart RoR wrote:
> Can Modules extends within themselves?
>
> Like Class A < B is Valid, where B is another class
> Module X < Y is invalid, where Y is another module?

Not directly. But you can use #included like this:

irb(main):001:0> module A; end
=> nil
irb(main):002:0> module B
irb(main):003:1> def self.included(cl)
irb(main):004:2> cl.class_eval { include A }
irb(main):005:2> end
irb(main):006:1> end
=> nil
irb(main):007:0> class X
irb(main):008:1> include B
irb(main):009:1> end
=> X
irb(main):010:0> X.ancestors
=> [X, A, B, Object, Kernel, BasicObject]
irb(main):011:0>

Note however that the inheritance order is reversed. There are a number
of other ways to achieve what you want. The requirement does not seem
to come up very frequently though. So maybe it's not an issue as big as
you think.

Kind regards

robert

--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/
From: Smart RoR on 23 Mar 2010 18:00
Thanks robert.
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Posted via http://www.ruby-forum.com/.

From: Caleb Clausen on 23 Mar 2010 18:45
On 3/23/10, Robert Klemme <shortcutter(a)googlemail.com> wrote:
> On 03/23/2010 03:11 AM, Smart RoR wrote:
>> Can Modules extends within themselves?
>>
>> Like Class A < B is Valid, where B is another class
>> Module X < Y is invalid, where Y is another module?
>
> Not directly. But you can use #included like this:
>
> irb(main):001:0> module A; end
> => nil
> irb(main):002:0> module B
> irb(main):003:1> def self.included(cl)
> irb(main):004:2> cl.class_eval { include A }
> irb(main):005:2> end
> irb(main):006:1> end
> => nil
> irb(main):007:0> class X
> irb(main):008:1> include B
> irb(main):009:1> end
> => X
> irb(main):010:0> X.ancestors
> => [X, A, B, Object, Kernel, BasicObject]
> irb(main):011:0>
>
> Note however that the inheritance order is reversed. There are a number
> of other ways to achieve what you want. The requirement does not seem
> to come up very frequently though. So maybe it's not an issue as big as
> you think.

Am I missing something? Why not just include A from B? Like this:

irb(main):001:0> module A; end
=> nil
irb(main):002:0> module B include A end
=> B
irb(main):003:0> class X
irb(main):004:1> include B
irb(main):005:1> end
=> X
irb(main):006:0> X.ancestors
=> [X, B, A, Object, Kernel]
irb(main):007:0>

From: Smart RoR on 23 Mar 2010 19:03


In the end, I wanted to see A as ancestor of B.
No classes, only modules.
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