快速解包值

Question

因此，我在解包和选项方面遇到了一些问题。我正在使用Google Places，并将place.formattedAddress值twice...first从GMSAutocompleteViewController传递给一个UIView，以便在一个字符串中显示。然后，我想在用户确认地点后将place.formattedAddress传递给Firebase。我可以将所选的GMSPlace传递给UIView，但是一旦我调用confirmAddPlace()函数，它就会在> let placeID2 = place.placeID行崩溃，并给出"terminating with uncaught of type NSException“。我相信这与展开和可选选项有关……我对这个概念还有些陌生。感谢大家的帮助！

// 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

不要在中强制解包你的参数。您可以将它们设置为可选，也可以将它们用作其类型。

使其成为可选的：

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

为了按原样使用它们的类型：(但为此，您必须使用未包装的值调用此函数，如：confirmAddPlace(myPlace!))

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

但是如果你真的想坚持你的实现，那么你可以像这样交换：

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

如果你传递的place有可疑之处，这将从你的函数返回