SWIFT 懒加载

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?


    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
        self.window = UIWindow(frame: UIScreen.mainScreen().bounds)
        // Override point for customization after application launch.
        self.window!.backgroundColor = UIColor.whiteColor()
        
        self.window!.rootViewController = RootViewController()
        
        self.window!.makeKeyAndVisible()
        return true
    }
}

import UIKit

class RootViewController: UIViewController {
    // 懒加载(只调用一次)
    /**
     *  注意：1.必须用var
     *       2.闭包后面必须跟上（）
     */
    lazy var data:[String] = {
        ()->[String]
        in
        print("初始化数据")
        return ["123","456","789"]
    }()
    override func viewDidLoad() {
        super.viewDidLoad()
        
    }
    
    override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
        print(data)
        print(data)
        print(data)
    }
}

 

来源：https://www.cnblogs.com/lantu1989/p/5205441.html