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Swift 反向传值

这是一个工程，展示了如何在 VC 之间进行传值，包括正向传值、反向传值和无向传值。

本示例代码基于 Xcode 7 ，并使用Swift 2.0 写成。

Swift 反向传值

正向传值

RootVC:

let del:DelegateViewController = DelegateViewController()
del.positiveValue = title! // 正向传值
self.presentViewController(del, animated: true, completion: nil)

DelegateVC:

var positiveValue:String = String() // 正向传值，接收方

反向传值

反向传值包括 delegate 、闭包、KVO 和 Notification 四种种方式：

Delegate

RootVC:

@IBAction funcdelegateButtonDidTapped(sender: AnyObject) {
    ...
    del.delegate = self // 设置下一个VC的delegate为当前的rootVC
    ...
}

//实现delegate的方法
funcpassValue(str:String) {
    self.delegateTF.text = str
}

DelegateVC:

var delegate:delegateOfNegative? //定义具体的delegate

funcback(sender:UIButton) {
    let tf:UITextField = self.view.viewWithTag(10000) as! UITextField
    delegate?.passValue(tf.text!) // 调用delegate的传值方法passValue
    self.dismissViewControllerAnimated(true, completion: nil)
}

闭包

RootVC:

@IBAction funcblockButtonDidTapped(sender: AnyObject) {
    ...
    let blo:BlockViewController = BlockViewController()
    // 设置block中要传递的值的接收方式
    blo.passBlockValue = {
        (title:String) in
        self.positiveTF.text = title
    }
    self.presentViewController(blo, animated: true, completion: nil)
}

BlockVC:

var passBlockValue:((title:String) -> Void)? // 定义block，包含参数title

funcback(sender:UIButton) {
    let tf:UITextField = self.view.viewWithTag(10001) as! UITextField
    passBlockValue?(title:tf.text!) // 使用block传递title这个值
    self.dismissViewControllerAnimated(true, completion: nil)
}

KVO

KVO只要是监听的属性，不管是正向还是反向都会触发 observeValueForKeyPath 方法，在其中做相应的显示即可。

RootVC:

var kvc:KVOViewController = KVOViewController() // 全局的KVOvc方便在deinit时removeobserver

@IBAction funcKVOButtonDidTapped(sender: AnyObject) {
    kvc.k = kvo()
        
    // addObserver添加监听
    kvc.k.addObserver(self, forKeyPath: "title", options: [NSKeyValueObservingOptions.Old, NSKeyValueObservingOptions.New], context: nil)
    kvc.k.title = self.positiveTF.text!
    self.presentViewController(kvc, animated: true, completion: nil)
}

// 监听对象的属性或者实例变量发生变化，就自动调用该函数，执行相应操作
override funcobserveValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
    if keyPath == "title" {
        print(change!)
        var nv = change!
        let newvalue: AnyObject? = nv["new"]
        print("the new value is/(newvalue!)")
        self.positiveTF.text = "/(newvalue!)" // 将监听到的变化值赋值给TF来显示
    }
}

deinit {
    // removeObserver移除监听
    // add和remove必须对应，否则报错
    kvc.k.removeObserver(self, forKeyPath: "title", context: nil)
}

KVOVC:

//要监听的对象的定义
classkvo:NSObject{
    var ptitle : String = ""
    
    // dynamic修饰的即为可支持KVO
    dynamic var title : String {
        get {
            return self.ptitle
        }
        set {
            self.ptitle = newValue
        }
    }
    
    override init() {
        println("init")
    }
    
    deinit {
        println("deinit")
    }
}

funcback(sender:UIButton) {
    let tit = (self.view.viewWithTag(10003) as! UITextField).text

    k.title = tit! // 对监听的属性赋值会触发observeValueForKeyPath方法

    self.dismissViewControllerAnimated(true, completion: nil)
}

Notification

RootVC:

viewDidLoad:

// 注册一个通知
NSNotificationCenter.defaultCenter().addObserver(self, selector: "notifReceive:", name: "notifName", object: nil)

@IBAction funcNotificationButtonDidTapped(sender: AnyObject) {
    let noti:NotificationViewController = NotificationViewController()
    noti.positiveValue = self.positiveTF.text!
        
    self.presentViewController(noti, animated: true, completion: nil)    
}

// 每次调用对应name的postNotificationName方法会由selector处理
funcnotifReceive(notification:NSNotification) {
    self.positiveTF.text = "/(notification.object!)"
    print("notif :/(notification.name),/(notification.object!)")
}

deinit {
    ...
    // removeObserver移除对应name的通知
    NSNotificationCenter.defaultCenter().removeObserver(self, name: "notifName", object: nil)
}

NotificationVC:

funcback(sender:UIButton) {
    let tit = (self.view.viewWithTag(10004) as! UITextField).text
        
    // 发送一个通知，name要对应。单一数据可用object传，多个数据可以用dictionary放进userInfo传
    NSNotificationCenter.defaultCenter().postNotificationName("notifName", object: tit, userInfo: nil)
    
    self.dismissViewControllerAnimated(true, completion: nil)
}