快速解开价值

Question

所以我在解包和可选方面遇到了一些问题。我正在使用谷歌地点并传递两次place.formattedAddress值...首先从 GMSAutocompleteViewController 到 UIView 以显示在字符串中。然后我想在用户确认地点后将place.formattedAddress传递给Firebase。我能够将选定的 GMSPlace 传递到 UIView 中，但是一旦我调用 confirmAddPlace(( 函数，它就会在第行崩溃>让 placeID2 = place.placeID 并给我"终止与未捕获的 NSException 类型的异常"。我相信这与解包和可选有关......我对这个概念还是有些陌生的。感谢您的任何帮助！

// Pass GMSPlace to UIView string
    // MARK: GOOGLE AUTO COMPLETE DELEGATE
    func viewController(_ viewController: GMSAutocompleteViewController, didAutocompleteWith place: GMSPlace) {
        let placeID = place.placeID
        placesClient.lookUpPlaceID(placeID, callback: { (place, error) -> Void in
            if let error = error {
                print("lookup place id query error: (error.localizedDescription)")
                return
            }
            guard let place = place else {
                print("No place details for (placeID)")
                return
            }
            print("Place name (place.name)")
            print("Place address (place.formattedAddress)")
        })
        let selectedPlace = place.formattedAddress
        if let name = selectedPlace as String!
        {
            self.placeNameLabel.text = "Are you sure you would like to add (name) to your places?"
        }
        self.dismiss(animated: true, completion: nil)
        setupConfirmationPopUp()
    }
// user taps confirm button to send item to be updated in Firebase
    func confirmAddPlace(place: GMSPlace!) {
        let accessToken = FBSDKAccessToken.current()
        guard let accessTokenString = accessToken?.tokenString else { return }
        let credentials = FIRFacebookAuthProvider.credential(withAccessToken: accessTokenString)
        FIRAuth.auth()?.signIn(with: credentials, completion: { (user, error) in
            if error != nil {
                print("Something went wrong with our FB user: ", error ?? "")
                return
        }
// create place on tap pf confirm
            let placeID2 = place.placeID
            guard let place = place else {
                print("No place details for (placeID2)")
                return
            }
            let confirmedPlace = place.formattedAddress
            if let confirmedPlace = confirmedPlace as String!
            {
                self.placeNameLabel.text = "(confirmedPlace)"
            }
            let ref = FIRDatabase.database().reference().child("places")
            let childRef = ref.childByAutoId()
            let values = ["place": self.placeNameLabel.text, "name": user!.displayName]
            childRef.updateChildValues(values)
    })  
        animateOut()
    }

Answer 1

不要在 func 中强制解开参数。要么将它们设置为可选，要么将它们用作其类型。

对于可选：

func confirmAddPlace(place: GMSPlace?) {
    ...
    ...
    let placeID2 = place?.placeID
    ...
    ...
}

对于按原样使用它们的类型：(但为此，您必须使用解包的值调用此 func，例如：confirmAddPlace(myPlace!) (

func confirmAddPlace(place: GMSPlace) {
    ...
    ...
    let placeID2 = place.placeID
    ...
    ...
}

但是，如果您确实想坚持您的实现，那么您可以像这样交换：

guard let place = place else {
    return
}
let placeID2 = place.placeID

如果您传递的place有可疑之处，这将从您的 func 返回