Feature #1102
closedPrepend Module
Description
=begin
Currently when a module is included into a classes, it is appended to the class hierarchy (ie. the method lookup order). This of course makes sense, but there are times when it would be useful to prepend the module. For example:
class C
def x; "x"; end
end
module M
def x; '[' + super + ']'; end
end
class C
prepend M
end
C.new.x #=> "[x]"
One big advantage of this is being able to override methods in a safer way, rather than using alias or tricks like alias_method_chain.
=end
Updated by trans (Thomas Sawyer) over 15 years ago
=begin
On Feb 7, 10:42 pm, Roger Pack rogerdp...@gmail.com wrote:
Currently when a module is included into a classes, it is appended to the class hierarchy (ie. > the method lookup order). This of course makes sense, but there are times when it would be > useful to prepend the module. For example:
I suppose one [not too useful] hack at it could be something like
class Class
def insert_module_at_top mod
previous_ancestors = self.ancestors.select{|a| a.class == Module}
include mod
previous_ancestors.each{|a| include a.dup}
end
end#again we have to start with a module.
module Original
def x; '[' + super + ']'; end
endclass A
include Original
endmodulePrepend
def x; "x"; end
end
A.insert_module_at_topPrepend
puts A.new.x
=> [x]Perhaps what we're saying here is we wish we could "grab" methods from
classes, to be able to manipulate the hierarchy better? This is
possible with RubyParser, since you can basically get back to the
source of the method and thus copy it around, but not afaik with 1.9
Well, that's not really the issue here. The need is to wrap
previously defined instance methods. If every method were defined in a
module (something I have suggested in the past actually) then it would
not be needed.
The utility comes from doing AOP-esque coding. Consider modules that
can initialize values.
class X
end
module P
attr :p
def initialize
@p = []
super
end
end
class X
prepend P
end
X.new.p => []
T.
=end
Updated by marcandre (Marc-Andre Lafortune) about 15 years ago
- Assignee set to matz (Yukihiro Matsumoto)
=begin
=end
Updated by rogerdpack (Roger Pack) over 14 years ago
=begin
+1 for Module#prepend
=end
Updated by manveru (Michael Fellinger) over 14 years ago
=begin
+1 for Module#prepend
=end
Updated by mame (Yusuke Endoh) over 14 years ago
- Target version changed from 2.0.0 to 3.0
=begin
Hi,
This ticket was also discussed in the thread from [ruby-core:25208].
Module#prepend may be very significant feature not only to implementation
but also to Ruby's OO model itself.
Don't consider it just convenient method like Array's and String's.
So, in my opinion, this feature should not be included in 1.9.x.
We should discuss it towards 2.0.
Even if it will be included in 1.9.x, we need more discussion.
Just seeing clean example, you'll find it cool. But in fact, we must
also discuss many dirty things:
-
edge semantics
- prepend into embedded class
- prepend into singleton class
- collaboration with reflection
- collaboration with future expansion (e.g., classbox)
- etc.
-
implementation
- robustness
- binary compatibility
- expandability
- maintainability
- performance
I think it is difficult to discuss them without material. So, please
write a patch first if you really want.
--
Yusuke Endoh mame@tsg.ne.jp
=end
Updated by naruse (Yui NARUSE) about 13 years ago
- Project changed from Ruby master to 14
- Category deleted (
core) - Target version deleted (
3.0)
Updated by naruse (Yui NARUSE) about 13 years ago
- Project changed from 14 to Ruby master
Updated by mame (Yusuke Endoh) over 12 years ago
This feature is listed as matz's "must-have." [ruby-core:39837]
Are there any volunteers to be a facilitator, to create a prototype,
and/or, to study the semantics and implementation?
Sorry I'll have no time, and completely forgot the discussion.
___
_|*|_
(`_`)
m9
I WANT YOU
--
Yusuke Endoh mame@tsg.ne.jp
Updated by ko1 (Koichi Sasada) over 12 years ago
- Assignee changed from matz (Yukihiro Matsumoto) to ko1 (Koichi Sasada)
- Target version set to 2.0.0
Updated by ko1 (Koichi Sasada) over 12 years ago
- Assignee changed from ko1 (Koichi Sasada) to nobu (Nobuyoshi Nakada)
Nobu will commit it.
Updated by nobu (Nobuyoshi Nakada) over 12 years ago
- Status changed from Feedback to Closed
- % Done changed from 0 to 100
This issue was solved with changeset r36234.
Thomas, thank you for reporting this issue.
Your contribution to Ruby is greatly appreciated.
May Ruby be with you.
Module#prepend
- class.c (rb_prepend_module): prepend module into another module.
- eval.c (rb_mod_prepend): new method Module#prepend. [Feature #1102]