创建主入口 main.swift:

import UIKit

UIApplicationMain(
	Process.argc,Process.unsafeArgv,NSStringFromClass(MainApp),NSStringFromClass(MainAppDelegate)
)

创建 app.swift,对应 MainApp 和 MainAppDelegate 的实现:

import UIKit

class MainApp: UIApplication {
	override func sendEvent(event: UIEvent) {
		super.sendEvent(event)
	}
}

class MainAppDelegate: UIResponder,UIApplicationDelegate {

	var window: UIWindow?

	func application(app: UIApplication,didFinishLaunchingWithOptions opt: [NSObject: AnyObject]?) -> Bool {

		self.window = UIWindow(frame: UIScreen.mainScreen().bounds)

		self.window!.rootViewController = UIViewController()
		self.window!.backgroundColor = UIColor.whiteColor()
		self.window!.makeKeyAndVisible()

		self.window!.AddSubview {
			let label = UILabel(frame: self.window!.frame)
			label.textAlignment = .Center
			label.text = "你好,UIKit!"
			return label
		}

		return true
	}

}

extension UIView {
	func AddSubview(subview: ()->UIView) {
		self.addSubview(subview())
	}
}

运行效果: