Delphi on OSX: how to convert CFDictionaryRef to NSDictionary?

Question

According to Apple documentation CFDictionaryRef and NSDictionary are Toll-Free Bridged Types. However, I get an AV in the following code, which MIGHT be because the bridge does not work with Delphi.

DADiskCopyDescription returns a CFDictionaryRef, which I wrap to a NSDictionary. The pointer is not NIL, but when I access a function in the object, I get an AV:

function osxGetRootVolumeUUID: string;
var lNSDictionary: NSDictionary;
    lDisk: DADiskRef;
    lCFUrl: CFURLRef;
    lSession: DASessionRef;
    lUUID: CFUUIDRef;
begin
  result := '';
  lSession := DASessionCreate(nil);
  lCFUrl := TNSURL.OCClass.fileURLWithPath(StrToNSStr('/'));
  lDisk := DADiskCreateFromVolumePath(nil,lSession,lCFUrl);
  lNSDictionary := TNSDictionary.Wrap(DADiskCopyDescription(lDisk));

  lUUID := lNSDictionary.objectForKey(kDADiskDescriptionVolumeUUIDKey); //<- AV here

  if lUUID<>nil then
    result := CFStringRefToStr( CFUUIDCreateString(nil, lUUID));
  lNSDictionary.release;
  CFRelease(lCFurl);
end;

I also tried to use CFBridgingRelease as suggested in this SO question but it gives error SIGABRT (6):

lNSDictionary := TNSDictionary.Wrap(CFBridgingRelease(DADiskCopyDescription(lDisk))); //gives error: SIGABRT (6)

How to make it work?

PS. Basically I just want to get the UUID of the root volume on OSX. The function above is converted to Delphi from an Objective-C function we have used so far.

Edit

Another thing I have tried is to avoid using NSDictionary, but this gives an error too, which could indicate that the problem is something else:

lCFDictionaryRef := DADiskCopyDescription(lDisk);
lUUID := CFDictionaryGetValue(lCFDictionaryRef, kDADiskDescriptionVolumeUUIDKey); //<- AV here

score 1 · Accepted Answer · answered Jun 09 '17 at 08:07

1

To convert a CFDictionaryRef to a TNSDictionary you must do it like this :

  var LNSDict: NSDictionary;
      LCFDict: CFDictionaryRef;

  LCFDict := DADiskCopyDescription(lDisk);
  try
    LNSDict:= TNSDictionary.Wrap(LCFDict );
  finally
    CFRelease(LCFDict);
  end;

so everything is good here, however i think maybe your av is in the way you access the object. don't forget in IOS to always use getObjectID and not the pointer to the object

ex: pass to ios api (xxx as ILocalObject).GetObjectID and never pass to the IOS api directly xxx

so maybe it's must be (kDADiskDescriptionVolumeUUIDKey as ILocalObject).GetObjectID or something similar

answered Jun 09 '17 at 08:07

zeus

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Thank you for your reply. Unfortunately kDADiskDescriptionVolumeUUIDKey cannot be typecasted to iLocalObject ([dccosx Error] uOSXutils.pas(136): E2015 Operator not applicable to this operand type). kDADiskDescriptionVolumeUUIDKey is generated by SDKtransform and I think it can be passed directly. – Hans Jun 16 '17 at 09:54
I just found that "(kDADiskDescriptionVolumeUUIDKey as ILocalObject).GetObjectID" was in fact the solution. The reason it did not work in the first place was that `kDADiskDescriptionVolumeUUIDKey` is implemented wrong in `Macapi.DiskArbitration`. When I implement it using `CocoaNSStringConst` instead of `CocoaPointerConst` then it works. – Hans Jan 23 '18 at 12:21

Delphi on OSX: how to convert CFDictionaryRef to NSDictionary?

1 Answers1