Protocol declaration in Swift - Xcode 6 beta 5

Question

With Xcode 6 beta 5 protocol and delegate doesn't work like first. printCar() is not invoked when self.delegate?.printCar() it's called. How can I use protocol & delegate now?

import UIKit

protocol communication{
    func printCar()
}

class car{
    var delegate:communication?

    init(){}

    func passCar(){
        self.delegate?.printCar()
    }
}

class ViewController: UIViewController,communication {

    override func viewDidLoad() {
        super.viewDidLoad()
        println("start")
        var bmw = car()
        bmw.passCar()
    }

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

    func printCar(){
        println("car")
    }
}

`self.delegate` is `nil` when `init()` is called. - (In fact you nowhere set the delegate to the view controller class.) — Martin R, Aug 21 '14 at 17:50
My last remark still applies (also in the answer below): You don't assign a delegate (such as `bmw.delegate = self`). — Martin R, Aug 21 '14 at 18:00

rickster · Accepted Answer · 2014-08-21T18:09:36.580

2

You aren't setting the car's delegate property, so there's no object to call printCar() on.

Also, it's convention to use initial caps for type names in Swift. (You'll notice that it's such strong convention that even SO's syntax highlighter expects it.)

BTW, it has nothing to do with this issue, but you might want to be on Xcode 6 beta 6 by now.

Another unrelated issue: Your car class's delegate property should probably be marked as weak. Otherwise, if the car's delegate is the object that owns the car, you get a memory leak.

edited Aug 21 '14 at 18:09

answered Aug 21 '14 at 17:51

rickster

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Before you call `bmw.passCar()`, you need to assign something to `bmw`'s `delegate` property. Otherwise the `self.delegate?.printCar()` call in that method won't execute, because `self.delegate?` resolves to `nil`. – rickster Aug 21 '14 at 18:06

Protocol declaration in Swift - Xcode 6 beta 5

1 Answers1