NSNotification addObserver selector could not open a NSBeginAlertSheet sheet on window - objective-c

Question

I have two different window Controllers. First is a custom panel window controller and another is main window controller. In panel window there is a panel window and there are button on that panel. On click of those buttons I am posting notification like :
In PanelWindowController:
-(IBAction)okAndCancelButtonClicked:(id)sender
{
[self postNotification:sender];
}
-(void)postNotification:(id)sender
{
if([sender tag]!=2){
[[self window] endSheet:self.panel returnCode:NSModalResponseCancel];
[self.panel orderOut:self];
}
NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithInteger:[sender tag]],#"value",nil];
[[NSNotificationCenter defaultCenter] postNotificationName:#"PanelButtonClickedNotification" object:self userInfo:dict];
}
Now, in my main window controller, I am trying to open a NSBeginAlertSheet in the selector of addObserver of NSNotificationCenter. Following is the addObserver selector declaration in init method of my main window controller:
MainWindowController
-(id) init{
..// some code here
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(okButtonClicked:) name:#"PanelButtonClickedNotification" object:[self panelClass]];
return self;
}
the implementation of okButtonClicked is the following :
- (void) okButtonClicked:(NSNotification*)notification
{
if ([[notification object] isEqualTo:[self panelClass]])
{
if([[[notification userInfo] objectForKey:#"value"] integerValue] == 1)
{
// Yes Button in the Panel is clicked
}
else if([[[notification userInfo] objectForKey:#"value"] integerValue] == 0)
{
// No Button in the Panel is clicked
NSBeginAlertSheet(#"Alert", #"Ok", nil, nil, [[self view] window], self,nil, nil,nil,#"Alert is being shown on window.");
}
}
}
When user clicks No button on Panel, an alert on the window should be displayed. But the alert is never shown. I also tried [NSApp keyWindow] and [NSApp mainWindow] instead of [[self view] window].
And, If I run the alert independently of window, it is displayed:
NSAlert *alert = [[NSAlert alloc] init];
[alert setMessageText:#"Alert"];
[alert addButtonWithTitle:#"OK"];
NSImage *icon=[NSImage imageNamed:#"warning.png"];
[alert setIcon:icon];
[alert runModal];
Please let me know if I am missing anything here.
The alert is not displayed in any of the methods called after the notification is received.
PFA my sample project : https://www.dropbox.com/s/0xfe4bk17v9girj/PanelApplication.zip?dl=0

Answer 1

It is a little difficult to tell, but my best guess would be, that the object that reacts to the notification, in the okButtonClicked: function, does not have a (valid) reference to your window. And then, the alert don't know on what window to display.
If you can send a reference to your window in the notification object, then you should be able to get the alert shown on the window you want.
example code:
[[NSNotificationCenter defaultCenter] postNotificationName:#"PanelButtonClickedNotification" object:[self window]];
And:
- (void) okButtonClicked:(NSNotification*)notification
{
NSBeginAlertSheet(#"Alert", #"Ok", nil, nil, [notification object], self,nil, nil,nil,#"Alert is being shown on window.");
}
this works in my test-project.

Answer 2

The problem was not with the notifications, it was the panel which was causing problems:
I was opening the panel in my main window controller:
[[self window] beginSheet:self.panelClass.panel completionHandler:nil];
And the closing action of the panel was written in the Panel window controller. Because of this reason no NSBeginAlertSheet was not being shown once the custom panel was loaded/ unloaded on the main window.
Therefore moving the following piece of code from panel window controller to main window controller solved the problem:
[[self window] endSheet:self.panelClass.panel returnCode:NSModalResponseCancel];
[self.panelClass.panel orderOut:self];