iOS页面回传值 -Delegate/Block/NSNotification/单例

1.Delegate:

https://www.crs811.com/index.php/2016/10/20/swift-protocol-delegate-callback/

2.Block:

https://www.crs811.com/index.php/2016/10/21/swift-closure/

3.NSNotification

首页：

    let ObServerName = "crs811"    
    weak var observe : NSObjectProtocol?

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.        

        NotificationCenter.default.addObserver(self, selector: #selector(ViewController.change), name: NSNotification.Name(rawValue: ObServerName), object: nil)        
        
        // name:    通知名字
        // object:  谁发出的通知，一般传nil
        // queue:   队列:表示决定block在哪个线程中去执行，nil表示在发布通知的线程中执行
        // using:   只要监听到了，就会执行这个block       
        observe = NotificationCenter.default.addObserver(forName: Notification.Name.init(rawValue: ObServerName), object: nil, queue: nil) { (Notification) in
            //print("-------------",Thread.current)
            
            let name = Notification.name
            
            //let userInfo = notification.userInfo as! [String:Any]
            guard let userInfo = Notification.userInfo else { return }
            
            let userInfoDic = userInfo as NSDictionary
            
            if name == NSNotification.Name(rawValue: self.ObServerName){                
                self.txtStuNO.text = userInfoDic.object(forKey: "name") as! String   
            }            
        }        
    }
    
    func change(notification: Notification) {       
        let name = notification.name
        
        //let userInfo = notification.userInfo as! [String:Any]
        guard let userInfo = notification.userInfo else { return }
        
        let userInfoDic = userInfo as NSDictionary
        
        if name == NSNotification.Name(rawValue: self.ObServerName){            
            self.txtStuNO.text = userInfoDic.object(forKey: "name") as! String   
        }
        
    }
    
    // 一定要移除，不移除的话会存在坏内存访问，移除的话需要定义一个属性observe来接收返回对象，然后在移除方法中移除即可
    deinit{
        // 移除通知
        NotificationCenter.default.removeObserver(self)
        NotificationCenter.default.removeObserver(observe!)
    }

    @IBAction func btnSec(_ sender: UIButton) {        
        let main = UIStoryboard(name: "Main", bundle: nil)
        let vc = main.instantiateViewController(withIdentifier: "SecViewController") as! SecViewController
        
        self.present(vc, animated: true, completion: nil)
    }

次页：

    let ObServerName = "crs811"

    @IBAction func btnBack(_ sender: UIButton) {    
        
        NotificationCenter.default.post(
            name: NSNotification.Name(rawValue: ObServerName),
            object: self,
            userInfo: ["name": self.txtStuNO.text]) //回传的用户数据，Dictionary, Image, NSData, ...
        
        self.dismiss(animated: true, completion: nil)    
    }

4. KVO

http://www.jianshu.com/p/e036e53d240e
http://www.cnblogs.com/JuneWang/p/3850859.html

5. 单例

Model Class:
创建单例：

 
final class Single: NSObject {  

    //使用全局变量创建单例
    static let shared = Single()  
    private let name = ""
    private override init() {}  

    //类方法，使用结构体创建单例 
    class func shareInstance() -> Single {  
        struct single{  
            static var g_Instance = Single()  
        }  
        return single.g_Instance  
    }  
}

首页：

let data = Single.shared  //Single.shareInstance()

if (data.name.length != 0) {
    self.nameLabel.text = data.name
}

次页：

let data = Single.shared

data.name = self.nameTextField.text;