8 messages in net.java.dev.rococoa.usersRe: nil| From | Sent On | Attachments |
|---|---|---|
| Duncan McGregor | Jul 17, 2009 8:01 am | |
| David Kocher | Jul 17, 2009 8:40 am | |
| Duncan McGregor | Jul 17, 2009 9:14 am | |
| David Kocher | Jul 17, 2009 3:52 pm | |
| Harald Kuhr | Jul 18, 2009 3:40 am | |
| Andrew Thompson | Jul 18, 2009 4:54 am | |
| Andrew Thompson | Aug 7, 2009 8:21 pm | |
| Duncan McGregor | Aug 10, 2009 8:00 am |
| Subject: | Re: nil | |
|---|---|---|
| From: | Duncan McGregor (dun...@oneeyedmen.com) | |
| Date: | Jul 17, 2009 9:14:27 am | |
| List: | net.java.dev.rococoa.users | |
On 17 Jul 2009, at 16:40, David Kocher wrote:
On 17.07.2009, at 17:01, Duncan McGregor wrote:
I'm canvassing opinion on Rococoa's handling of nil.
As I understand it, ObjC silently ignores messages sent to nil, whereas Java throws NullPointerException if you try to invoke a method on null.
I'm trying to decide what I think, but here is a taster of the issues - if you call a ObjC method that is defined to return an NSObject, and the returned value is actually nil, should that return a Java null, or an instance of our Java NSObject that has nil inside it?
It should definitly return null. It makes programming against the API a lot more intuitive than to check for isNil() on the NSObject. See my patch sent to the dev list for NSInvocationMapper.
I was thinking of the cases where you get a nil back from Cocoa and then pass it into another Cocoa method, but I guess in that case we'll just convert null to nil and no-one will notice.
If the latter, should invoking methods on the Java NSObject throw NullPointerException (they currently do - is anyone relying on that behaviour) or pass down to ObjC to be silently ignored?
Yes, I would expect that.
You expect the throwing or the ignoring?
Does anyone know what the Java/Cocoa bridge does?
It maps nil to null.
You were the _anyone_ I had in mind ;-)