Hi Caio, You found out an exception :) As you know, NSArray responds to -count which simply return the number of elements it contains. But Ruby Array defines #count which has different semantics. To not conflict with NSArray, the Ruby #count is only defined on Ruby arrays. However, I do not understand where #count is used in your snippet. Is it used in Pathname? Laurent On Oct 4, 2010, at 12:14 AM, Caio Chassot wrote:

Hi all,

Code first:

cocoa_array = NSArray.new ruby_array = []

puts ruby_array.count # => 0 puts ruby_array.count { true } # => 0 puts ruby_array.count("whatever") # => 0

puts cocoa_array.count # => 0 puts cocoa_array.count { true } # => 0 # unknown: warning: passing a block to an Objective-C method - will be ignored puts cocoa_array.count("whatever") # => wrong number of arguments (1 for 0) (ArgumentError)

I originally ran into this issue in the following code, where the fact that we have an NSArray, and not a ruby array ends up concealed by the bajillion of ruby-ish method calls such as compact and map:

paths_from_clipboard = NSPasteboard.generalPasteboard.pasteboardItems .map { |pbi | pbi.stringForType('public.file-url') }.compact .map { |url | NSURL.URLWithString(url).path } .map { |path| Pathname.new(path) }

Full, pretty and colorful version: http://gist.github.com/602174

What's going on there is that NSArrays (but not NSMutableArrays) will use the vanilla Cocoa's count method.

So I'm resorting to doing:

Array.new(SomeCocoaClass.withAMethodThatReturnsAnNSArray)

I wonder, is this a bug or "works as designed"?

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