Re: [Rubycocoa-talk] Programmatically overriding 0-arity ObjC methods

[sergio <sde...@gm...>]

On 29/ago/07, at 01:18, Laurent Sansonetti wrote:

>> this is my first post to this list.
>
> Welcome!

thanks!

>> [...]
>> /Library/Frameworks/RubyCocoa.framework/Versions/A/Resources/ruby/ 
>> osx/
>> objc/oc_import.rb:318:in `_ns_behavior_method_added': Cannot override
>> Objective-C method 'awakeFromInsert' with Ruby method
>> #awakeFromInsert, they should both have the same number of arguments.
>> (expected arity 0, got -1) (RuntimeError)

> The problem here is that an empty block (proc {}) has an arity of -1,
> for an unknown reason.  But a block with an empty argument list (proc
> {||}) will have an arity of 0. So normally if you call define_method
> with blocks with an empty argument list, you should not get the
> exception.

perfect! it works with an empty argument list...

I did some googling and I found that the arity conventions in ruby  
1.9 could change... I don't know what is the official source of  
information about 1.9, but I found this interesting:

(1) http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/120252
(2) http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/11029? 
help-en
(3) http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/249149

in short, it seems that in 1.9 both proc{}.arity and proc{||}.arity  
shall return 0 -- by definition (1) -- although it seems (3) that in  
some not so old ruby 1.9.0 release both returned -1. in any case,  
this would be a change from how it works now. if what I am saying is  
just crap, simply ignore it... :-)

best
sergio