Is it possible to subclass NSSavePanel?

Question

I am wondering if there is a way to subclass NSSavePanel. Or if you were to create a dummy object, how would you mimic the beginSheetModalForWindow:CompletionHandler function of NSSavePanel?

-(void)beginSheetModalForWindow:(NSWindow *)window completionHandler:(void (^)(NSInteger *))handler{

I am blanking out on how to implement the block handler when implementing the function in the .m class file.

Answer 1

Short Answer: No

Longer Answer: Here Be Dragons

It is possible but stuff will probably break. You can also add methods using a category and they might work, or they might not. The problems arise due to the way NSOpenPanel is implemented to support the App Sandbox - various chicanery is going on behind the scenes and even convenience category methods which just call existing methods on the class can result in errors being reported by OS X and dialogs not to appear. NSOpenPanel is a delicate creature that should be touched as little as possible and only ever with great care.

Wrapping an NSOpenPanel instance in another class is a different story and should not upset it at all. Go that route.

Addendum re: Comment

The declaration of beginSheetModalForWindow is:

- (void)beginSheetModalForWindow:(NSWindow *)window completionHandler:(void (^)(NSInteger result))handler

The completion handler gets passed a value indicating which button was pressed. To take action dependant on that you can use a standard if:

NSOpenPanel *openPanel;
NSWindow *hostWindow;
...
[openPanel beginSheetModalForWindow:hostWindow
                  completionHandler:^(NSInteger returnCode)
                                    {
                                       if (returnCode == NSFileHandlingPanelOKButton)
                                       {
                                          // OK pressed
                                          ...
                                       }
                                       else
                                       {
                                          // Cancel pressed
                                          ...
                                       }

                                    }
];