Can't see a new subview - objective-c

Question

All I am trying to do is add a new view to the content view of my NSWindow instance. When I do the following I do not see the new view (which should be black and take up the entire window). What am I doing wrong?
(done in response to a button click)
NSRect frameRect = [self.window frame];
frameRect.origin = NSZeroPoint;
NSView *view = [[NSView alloc] initWithFrame:frameRect];
view.wantsLayer = YES;
view.layer.backgroundColor = [NSColor blackColor].CGColor;
[self.window.contentView addSubview:view];

Answer 1

I've set up a simple project with a push button inside a ViewController and got a warning for accessing self.window. When using self.view.windowthe warning went away and your provided code works as expected.
Updated code
NSRect frameRect = [self.view.window frame];
frameRect.origin = NSZeroPoint;
NSView *view = [[NSView alloc] initWithFrame:frameRect];
view.wantsLayer = YES;
view.layer.backgroundColor = [NSColor blackColor].CGColor;
[self.view.window.contentView addSubview:view];
Update
Assuming that you're using an instance of WindowController where you're adding a button programmatically, your code works as expected.
#implementation WindowController
- (void)windowDidLoad
{
[super windowDidLoad];
CGRect buttonRect = CGRectMake(self.window.frame.size.width / 2 - 50,
self.window.frame.size.height / 2,
100,
50);
NSButton *button = [[NSButton alloc] initWithFrame:NSRectFromCGRect(buttonRect)];
[button setTitle: #"Click me!"];
[button setTarget:self];
[button setAction:#selector(buttonPressed)];
[self.window.contentView addSubview:button];
}
- (void)buttonPressed
{
NSRect frameRect = [self.window frame];
frameRect.origin = NSZeroPoint;
NSView *view = [[NSView alloc] initWithFrame:frameRect];
view.wantsLayer = YES;
view.layer.backgroundColor = [NSColor blackColor].CGColor;
[self.window.contentView addSubview:view];
}
An instance of NSViewController ain't got a property of window - only NSWindowController has one.