Pfthb

I am able to return the screen size using:

- (void) getScreenResolution 

 NSArray *screenArray = [NSScreen screens];
 NSScreen *mainScreen = [NSScreen mainScreen];
 unsigned screenCount = [screenArray count];
 unsigned index = 0;

 for (index; index < screenCount; index++)
 
 NSScreen *screen = [screenArray objectAtIndex: index];
 NSRect screenRect = [screen visibleFrame];
 NSString *mString = ((mainScreen == screen) ? @"Main" : @"not-main");

 NSLog(@"Screen #%d (%@) Frame: %@", index, mString, NSStringFromRect(screenRect));
 

Output:

Screen #0 (Main) Frame: 0, 4, 1344, 814

Is there a way to format 1344, 814 to 1344x814?

Edit:

This works perfectly:

- (NSString*) screenResolution 

 NSRect screenRect;
 NSArray *screenArray = [NSScreen screens];
 unsigned screenCount = [screenArray count];
 unsigned index = 0;

 for (index; index < screenCount; index++)
 
 NSScreen *screen = [screenArray objectAtIndex: index];
 screenRect = [screen visibleFrame];
 

 return [NSString stringWithFormat:@"%.1fx%.1f",screenRect.size.width, screenRect.size.height];

NSLog(@"%fx%f",screenRect.size.width, screenRect.size.height);

Finding the screen size in Mac OS is very simple:

NSRect e = [[NSScreen mainScreen] frame];
H = (int)e.size.height;
W = (int)e.size.width;

In Swift 4.0 you can get the screen size of the main screen:

if let screen = NSScreen.main 
 let rect = screen.frame
 let height = rect.size.height
 let width = rect.size.width

If you look for the size of the screen with a particular existing window you can get it with:

var window: NSWindow = ... //The Window laying on the desired screen
var screen = window.screen!
var rect = screen.frame
var height = rect.size.height
var width = rect.size.width

For those guy who are looking for a way to get screen resolution:

If you are programming a window based app, you can simply get the resolution from _window.screen.frame.size

edit/update

Swift 4

NSScreen.main?.frame // x 0 y 0 w 1,920 h 1,200
NSScreen.main?.frame.width // 1,920.0
NSScreen.main?.frame.height // 1,200.0 

Swift 3.x

NSScreen.main()?.frame // x 0 y 0 w 1,920 h 1,200
NSScreen.main()?.frame.width // 1,920.0
NSScreen.main()?.frame.height // 1,200.0 

Swift 2.x

NSScreen.mainScreen()?.frame // x 0 y 0 w 1,920 h 1,200
NSScreen.mainScreen()?.frame.width // 1,920.0
NSScreen.mainScreen()?.frame.height // 1,200.0

Swift 3 solution:

NSScreen.main()!.frame