On Apr 26, 2010, at 5:58 AM, Billy Flatman wrote: > I'm trying to put a custom object into past board in order to perform a drag > operation.
You can’t do that, for the same reason you can’t directly write a custom object to a file. The pasteboard basically stores bytes, so it has to be able to convert what you store in it to and from a stream of bytes. There are a limited number of data types it understands — strings, numbers, arrays, dictionaries and of course raw data. > ** This doesn't (actually stops drag and drop working for my > application until I logout). > [pboard setData:[items objectAtIndex:0] forType:kOutlineViewGroupType]; You’re passing the wrong type of object to the setData: parameter. Look at the header or the docs — it takes an NSData. You’re passing it some other custom object. The result is going to be an exception or a crash. (The reason this doesn’t produce a warning at compile time is because -objectAtIndex: just returns type id, which is compatible with anything (it’s like void* for objects.) You have to pay attention to what type of object you know is in the array. If you want to put a custom object in the pasteboard, there are several ways: (1) Wrap it in an NSValue via [NSValue valueWithPointer:]. This is kind of dangerous because you have to make sure the object won’t get dealloced before the pointer is eventually used, since -valueWithPointer: doesn’t retain the object. (2) Store some value that refers to the object, like a row number or an access key. You have to make sure that value will continue to work, i.e. the row number remains correct. (3) Implement a way to serialize the object into data or a dictionary/array. Implementing the NSCopying protocol is a standard way to do that. The first two techniques are OK for drag-n-drop because the lifetime of the pasteboard is limited. If you want to implement copy and paste you probably need to go with #3 because the pasteboard could stay around for an arbitrary amount of time. —Jens_______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
