Hi Brian, On May 29, 2008, at 6:07 AM, Brian Mitchell wrote:
I've been playing around with objects a bit and have noticed the Objective-C interfaces for object allocation are available. I'm not an regular Objective-C user so this is all from my limited knowledge.
In MacRuby, one can currently get away with something like NSCFString.alloc, and it seems to not cause any immediate crashes if init is not called right after. This is a dangerous assumption of course. If I simply try calling on a different class where init is more important it will quickly cause a crash: NSMutableString.alloc.size.
In Objective-C the pattern is (AFAICT) usually something like [[MyClass alloc] initOfSomeSort]. It makes sense and the responsibility is on the developer to keep things consistent. In Ruby code however, I would expect these sorts of issues to either be handled or be impossible to occur in pure Ruby. Now there might be a way to handle errors better (i.e. catching the NSInvalidArgumentException in the above example) and prevent bad crashes that currently occur but is this sort of thing just going to become a side effect of living on top of an Objective-C style class hierarchy and protocol? I'd really like to avoid getting segmentation faults and other lower level problems in Ruby code. (Though I don't mind paying the price if this gets to what 1.0 has promised. ;-) )
First of all, one thing that might be important to notice is that MacRuby runs in an Objective-C garbage collected environment. Which means that you can use the Objective-C interfaces to create objects, but there is no need to retain/release/autorelease objects. Regarding the [alloc [init ... pattern, it's unfortunately unavoidable. init must follow alloc, and there are many cases in Cocoa where not doing this will result in a very bad behavior (we experimented this in RubyCocoa). Trying to catch a potential exception might work in some cases, but fail in others (one example, NSView). Nevertheless, it is still possible to create objects with #new.
v = NSView.new # instead of NSView.alloc.initWithFrame(...) => #<NSView:0x2f9d060> v.frame => #<NSRect origin=#<NSPoint x=0.0 y=0.0> size=#<NSSize width=0.0 height=0.0>> v.frame = [1, 2, 3, 4] => [1, 2, 3, 4] v.frame => #<NSRect origin=#<NSPoint x=1.0 y=2.0> size=#<NSSize width=3.0 height=4.0>> v.subviews => [] v.addSubview NSButton.new => nil v.subviews => [#<NSButton:0x28aea50>]
Laurent