swift -NavigationController,代理传值

////  ViewController.swift//  NavigationController//import UIKitimport Foundationclass ViewController: UIViewController,FontSizeChangDelegate {    var  myLabel :UILabel?;//声明一个UILabel对象 全局的    override func viewDidLoad() {        super.viewDidLoad()        //self.title = "百度";        self.navigationItem.title = "百度";                let nextItem = UIBarButtonItem(title: "下一页", style: .Plain, target: self, action: "nextPage");        self.navigationItem.rightBarButtonItem = nextItem;                //放一个Label可以显示文字        let rect = CGRect(x: 0, y: 100, width: 320, height: 44);        myLabel = UILabel(frame: rect);        myLabel!.text = "欢迎来到百度";        self.view.addSubview(myLabel!);               // Do any additional setup after loading the view, typically from a nib.    }        func nextPage(){        NSLog("按钮被点击了");        let svc = SubViewController();                //设置这个协议                svc.delegate = self;        self.navigationController?.pushViewController(svc, animated: true);            }//  代理方法    func fontSizeDidChange(controller: SubViewController, fontSize: Int) {        println("controller is\(controller) fontsize:\(fontSize)");        let font = UIFont.systemFontOfSize(Float(fontSize));//这里有错误        myLabel!.font = font;    }    override func didReceiveMemoryWarning() {        super.didReceiveMemoryWarning()        // Dispose of any resources that can be recreated.    }}

////  SubViewController.swift//  NavigationController//import UIKitimport Foundation//定义一个协议protocol FontSizeChangDelegate:NSObjectProtocol{    //定义的一个协议函数/代理的一个函数    //参数1 当前controller本身    //参数2 字体大小    func fontSizeDidChange(controller:SubViewController,fontSize:Int);}class SubViewController: UIViewController {    var fontSize:Int = 20;    //定义一个delegate对象    var delegate:FontSizeChangDelegate?;    override func viewDidLoad() {        super.viewDidLoad()        self.view.backgroundColor = UIColor .whiteColor();                self.title = "Page2";        //self.backgroundColor = UIColor .whiteColor();        // Do any additional setup after loading the view.        var btn = UIButton.buttonWithType(.System) as UIButton;        var frame = CGRect(x: 100, y: 100, width: 100, height: 100);        btn.frame = frame;        btn.setTitle("增大字体大小", forState: .Normal);        btn.addTarget(self, action: "clickMe:", forControlEvents:.TouchUpInside);        self.view.addSubview(btn);    }    func clickMe(sender:UIButton){        //self.navigationController?.popToRootViewControllerAnimated(true);        fontSize++        println("fontsize is\(fontSize)");                if((delegate) != nil)        {            //调用里面的协议方法            delegate?.fontSizeDidChange(self,fontSize:fontSize);        }    }    override func didReceiveMemoryWarning() {        super.didReceiveMemoryWarning()        // Dispose of any resources that can be recreated.    }        /*    // MARK: - Navigation    // In a storyboard-based application, you will often want to do a little preparation before navigation    override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {        // Get the new view controller using segue.destinationViewController.        // Pass the selected object to the new view controller.    }    */}