[MacRuby-devel] NSArray's count and Ruby Array#count

[Caio Chassot]

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"?