From: Brian Marick <marick@...>
Date: 2008-12-18T23:13:54+09:00
Subject: Re: [RubyCocoa] C pointers, and documentation


On Dec 17, 2008, at 12:13 PM, Christophe Mckeon wrote:
>               error:(NSError **)outError
>
> is there a standard way of handling it? is this
> kind of thing documented anywhere?

There's a class called ObjcPtr that's used to translate to/from such  
arguments. Google around for that word and you'll find sketchy  
documentation. Here's an example of stuffing a value into such an  
"out" parameter:

def getObjectValue_forString_errorDescription(objptr, s, errdesc)
  case s.to_ruby.downcase
    when 'yes': objptr.assign(true)
    when 'no': objptr.assign(false)
    else return false
  end
  true
end

To pull an object out of a pointer-to-object, you do this:

  def observeValueForKeyPath_ofObject_change_context(
             keyPath, object, change, rawContext)
    context = rawContext.cast_as('@')
    puts "Context: #{context.inspect}"
  end

The '@' identifies the thing-being-pointed-to as an object. There are  
other symbols to identify things like raw machine integers, etc. I  
forget where you find them, but they're not RubyCocoa-specific, so  
they're somewhere in Apple documentation.

For non-objects there are also methods like "int_at", "bool_at",  
"bool", and "int". I haven't had reason to use them yet, so I don't  
know the details.

-----
Brian Marick, independent consultant
Mostly on agile methods with a testing slant
www.exampler.com, www.exampler.com/blog, www.twitter.com/marick

-----
Brian Marick, independent consultant
Mostly on agile methods with a testing slant
www.exampler.com, www.exampler.com/blog, www.twitter.com/marick