When building Mac applications, Apple usually takes care of most of the default behaviours for you. One thing that Mac applications don’t do by default is, reopening the applications main window (if it has been closed), when the dock icon is pressed.

Although this information is very hard to find in the documentation, but is actually very easy to. The method you need to find is:

- (BOOL)applicationShouldHandleReopen:(NSApplication *)theApplication hasVisibleWindows:(BOOL)flag;

This is an optional delegate method that your AppDelegate can choose to implement, and is called when the user presses your application’s dock icon. The bool flags indicates whether the application has any visible windows. To reopen your application’s main window, you need to have a pointer to it (In the example below assume that it is defined as NSWindow *window; in the header file). If you do have a pointer to then you simple need to implement the code below.

- (BOOL)applicationShouldHandleReopen:(NSApplication *)theApplication hasVisibleWindows:(BOOL)flag {

    if (flag == NO) {
        [window makeKeyAndOrderFront:self]; 
    }
    return YES; 
}

It is as simple as that.