Why is my code only working the second time around? Delegate issue? - objective-c

Question

In Objective-C, I am trying to make a NSTextField, when clicked, open a sheet with a NSDatePicker that slides out under the text field. You select a date which closes the sheet and populates the NSTextField with the date chosen.
I have found this article on how to use a protocol to do this in Swift. http://www.knowstack.com/swift-nsdatepicker-sample-code/#comment-20440
But when I convert it to Objective-C I have a few issues.
The first time I click my button to trigger the sheet, the sheet appears in the middle of the screen, ignoring the event:
-(NSRect)window:(NSWindow *)window willPositionSheet:(NSWindow *)sheet usingRect:(NSRect)rect {
When I select a date, the textfield in the main xib is updated with the selection so the protocol part is working but the sheet remains unresponsive on screen.
If I click the button a second time, the unresponsive sheet closes and reappears under the NSTextField and dismisses itself when I choose a date. This is the expected behaviour.
My question is, why does this not work the first time I click the button but only works the second time?
Here is the code:
#import <Cocoa/Cocoa.h>
#protocol DatePickerProtocol
#required
-(void) selectedDate:(NSDate *)date;
#optional
#end
#interface datePickerWindowController : NSWindowController {
id delegate;
}
-(void)setDelegate:(id)newDelegate;
#end
#import "datePickerWindowController.h"
#interface datePickerWindowController ()
#property (weak) IBOutlet NSDatePicker *datePicker;
#end
#implementation datePickerWindowController
- (void)windowDidLoad {
[super windowDidLoad];
self.datePicker.dateValue = [NSDate date];
}
-(void)setDelegate:(id)newDelegate {
delegate = newDelegate;
NSLog(#"delegate has been set in datePickerWindowController");
}
- (IBAction)selectDate:(NSDatePicker *)sender {
[delegate selectedDate:self.datePicker.dateValue];
[self.window close];
}
#end
#import <Cocoa/Cocoa.h>
#import "datePickerWindowController.h"
#interface AppDelegate : NSObject <NSApplicationDelegate, DatePickerProtocol, NSWindowDelegate>
#end
#import "AppDelegate.h"
#interface AppDelegate ()
#property (weak) IBOutlet NSWindow *window;
#property (weak) IBOutlet NSDatePicker *timePicker;
#property (weak) IBOutlet NSTextField *textDate;
#property (retain) datePickerWindowController * myDatePickerWindowController;
#end
#implementation AppDelegate
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
self.window.delegate = self;
[self.window setDelegate:self];
self.textDate.stringValue = [NSString stringWithFormat:#"%#",[NSDate date]];
datePickerWindowController * windowController = [[datePickerWindowController alloc] initWithWindowNibName:#"datePickerWindowController"];
self.myDatePickerWindowController = windowController;
self.myDatePickerWindowController.delegate = self;
[self.myDatePickerWindowController setDelegate:self];
}
- (void)applicationWillTerminate:(NSNotification *)aNotification {
}
-(void)selectedDate:(NSDate *)date {
self.textDate.stringValue = [NSString stringWithFormat:#"%#", date];
}
- (IBAction)pickDateButton:(NSButton *)sender {
[self.window beginSheet:self.myDatePickerWindowController.window completionHandler:nil];
}
// Position sheet under text field
-(NSRect)window:(NSWindow *)window willPositionSheet:(NSWindow *)sheet usingRect:(NSRect)rect {
if (sheet == self.myDatePickerWindowController.window) {
NSRect r = self.textDate.frame;
r.origin.y = r.origin.y + 5;
return r;
} else {
return rect;
}
}
#end
I am assuming I have the delegate messed up somehow. Maybe in the xib or the code. I can not see why it works a second time though. Is this due to retain or how I am keeping the DatePicker around.
Many thanks for any help.