[MacRuby-devel] NSManagedObject being returned in delegate as Pointer

[Nic Williams]

Calling recipe[0] results in this error:

AppDelegate.rb:157:in `[]': can't convert C/Objective-C value
`0x8004676a0' of type `v' to Ruby object (ArgumentError)

I'm not sure what this means. I've played around with the Pointer
class and I can get this error a lot.

The original ObjC signature that is called to open the NSOpenPanel is:

- (void)beginSheetForDirectory:(NSString *)path file:(NSString *)name
modalForWindow:(NSWindow *)docWindow modalDelegate:(id)modalDelegate
didEndSelector:(SEL)didEndSelector contextInfo:(void *)contextInfo

Where the recipe (NSManagedObject_Recipe) is passed into a (void
*)contextInfo. Do I need to do anything fancy for this? Is the (void
*) causing the Pointer creation?

On Wed, Dec 31, 2008 at 1:46 PM, Laurent Sansonetti
<lsansonetti at apple.com> wrote:
> On Dec 30, 2008, at 7:32 PM, Nic Williams wrote:
>
>> In this code sample: http://gist.github.com/41855 I am getting a
>> Pointer instance instead of an NSManagedObject_Recipe instance (from
>> Core Data). Subsequently the setValue:forKey: call at the end of the
>> delegate/callback method fails.
>>
>> The top method addImage(sender) launches an NSOpenPanel, which
>> delegates to the second/last method
>> addImageSheetDidEnd:returnCode:contextInfo: when the panel is closed.
>>
>> But instead of passing through the NSManagedObject_Recipe instance to
>> the contextInfo: recipe value, I am getting a Pointer.
>>
>> Is this correct? Or how do I get my NSManagedObject_Recipe instance
>> from the Pointer. MacRuby src for Pointer class doesn't suggest it has
>> any methods for getting the pointed-to thing.
>>
>>   rb_cPointer = rb_define_class("Pointer", rb_cObject);
>>   rb_undef_alloc_func(rb_cPointer);
>>   rb_define_singleton_method(rb_cPointer, "new_with_type",
>> rb_pointer_new_with_type, 1);
>>   rb_define_method(rb_cPointer, "assign", rb_pointer_assign, 1);
>>   rb_define_method(rb_cPointer, "[]", rb_pointer_aref, 1);
>
> You can do pointer[0] to dereference it.
>
> A Pointer object can be created from a C array of elements, which is why
> Pointer responds to #[] (so that you can dereference a particular slot).
>
> Laurent
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>



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