swift delegate beetween two view controller without segue

问题

My delegate protocol never called

My first controller - ViewController

class ViewController: UIViewController,testProtocol {

    @IBAction func btInit(sender: AnyObject) {
        println("Bt Init")

        let storyBoard : UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
        let initViewController: UIViewController = storyBoard.instantiateViewControllerWithIdentifier("viewTarget") as targetViewController
        self.presentViewController(initViewController,animated: false, nil)

    }

    var targetController = targetViewController();

    override func viewDidLoad() {
        super.viewDidLoad()
        self.targetController.delegate = self
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func testDelegate(){
        println(" in my view controller delegate ")
    }
}

In my second view controller - targetViewController

protocol testProtocol {
    func testDelegate() // this function the first controllers
}

class targetViewController: UIViewController {

    @IBAction func BtTarget(sender: AnyObject) {

        println("bt target pressed")

        delegate?.testDelegate()
    }

    var delegate : testProtocol?

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }

    func testDelegate(){
        println(" in my target view controller delegate ")
    }
}

Why is testDelegate() never called on ViewController? What am I doing wrong? Thanks.

I have read a lot of posts about this, but all of the examples are given with segue transition, and I don't want use a segue.

回答1:

Typically you set a new view controller's delegate property in prepareForSegue:. You said you're not using a segue, so you'll need to instantiate the second view controller and present it somehow. You can do this by doing something like:

let storyboard = UIStoryboard(name: "AStoryboardName", bundle: nil)
let secondVC = storyboard.instantiateViewControllerWithIdentifier(anIdentifier) as! targetViewController
secondVC.delegate = self
presentViewController(secondVC, animated: true, completion: nil)

You have a testDelegate() method in both view controllers, but you only want it in the first view controller. Then your second view controller can call delegate?.testDelegate() at the appropriate time.

Finally, you typically want to make delegate properties weak, so I would recommend changing var delegate : testProtocol? to weak var delegate: testProtocol?

I would read up on delegation. Here is a relatively simple 5 step process to delegation that may help you:

Delegation in 5 Steps:

object A is the delegate for object B, and object B will send out the messages:

1. Define a delegate protocol for object B.
2. Give object B an optional delegate variable. This variable should be weak.
3. Make object B send messages to its delegate when something interesting happens, such as the user pressing the Cancel or Done buttons, or when it needs a piece of information.
4. Make object A conform to the delegate protocol. It should put the name of the protocol in its class line and implement the methods from the protocol.
5. Tell object B that object A is now its delegate (in prepareForSegue(sender)).

来源：https://stackoverflow.com/questions/31222275/swift-delegate-beetween-two-view-controller-without-segue