How do I set Different Storyboards for each possible screen size in Swift?

I already have the Objective-C code.

Please, no Auto Layout, I don't need it.

But how do I convert it to Swift? I am new to Swift.

Here is code for Objective-C:

**AppDelgate.m** file

```
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.

    // int screenHeight = [UIScreen mainScreen].bounds.size.height;
    // NSLog(@"Screen Height is %i", screenHeight);

    // grab correct storyboard depending on screen height
    UIStoryboard *storyboard = [self grabStoryboard];

    // display storyboard
    self.window.rootViewController = [storyboard instantiateInitialViewController];
    [self.window makeKeyAndVisible];

    return YES;
}

- (UIStoryboard *)grabStoryboard {
    // determine screen size
    int screenHeight = [UIScreen mainScreen].bounds.size.height;
    UIStoryboard *storyboard;

    switch (screenHeight) {
            // iPhone 4s
        case 480:
            storyboard = [UIStoryboard storyboardWithName:@"Main-4s" bundle:nil];
            break;

            // iPhone 5s
        case 568:
            storyboard = [UIStoryboard storyboardWithName:@"Main-5s" bundle:nil];
            break;

            // iPhone 6
        case 667:
            storyboard = [UIStoryboard storyboardWithName:@"Main-6" bundle:nil];
            break;

            // iPhone 6 Plus
        case 736:
            storyboard = [UIStoryboard storyboardWithName:@"Main-6-Plus" bundle:nil];
            break;

        default:
            // it's an iPad
            storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
            break;
    }
    return storyboard;
}

```