无法转换期望参数类型GTLServiceCompletionHandler的值

Question

I wrote my app in Swift 2.3.Using Google Cloud AppEngine. Now I upgraded to xCode8.0 and need to convert my app to Swift 3.0. The following code is correct in Swift 2.3. But it is wrong in Swift 3.0. Any help would be appreciated! issue: Cannot convert value of type '(GTLServiceTicket!, GTLObject!, NSError!) -> Void' to expected argument type 'GTLServiceCompletionHandler!'

func sendRequest() -> GTLServiceTicket? {
    if self.query != nil && shouldSend {
        self.ticket = appService.executeQuery(query!, completionHandler: {
            (ticket: GTLServiceTicket!, object: AnyObject!, error: NSError!) -> Void in
            if error != nil {
                for handler in self.onFailure {
                    handler(ticket, error)
                }
            } else {
                for handler in self.onSuccess {
                    handler(ticket, object)
                }
            }
        })
    }
    return ticket
}

Answer 1

You need to do some changes to your code specially if your jumping to #Swift 3.0 #Xcode 8

things to remember :-

• NS is removed from most places eg NSError has become Error

• Also now id parameter from objective-c will have type Any in swift3.

So coming back to the question, Previously, if parameters in objective-c code did not have nullability attributes(like nonnull or nullable), Swift converts it with ! making them non optional(forced unwrapping). Now it convert it with ? making them optional. Thats why you are getting an error. The completion handler will become :

func sendRequest() -> GTLServiceTicket? { if self.query != nil && shouldSend { self.ticket = appService.executeQuery(query!, completionHandler: { (ticket: GTLServiceTicket?, object: Any?, error: Error?) -> Void in if error != nil { for handler in self.onFailure { handler(ticket, error) } } else { for handler in self.onSuccess { handler(ticket, object) } } }) } return ticket }

Answer 2

Thank you for your answer! I have tried it. The following two codes are working. All need add "as Optional 'NSError'" and "as Optional 'AnyObject'"

1.

func sendRequest() -> GTLServiceTicket? {
    if self.query != nil && shouldSend {
        self.ticket = appService.executeQuery(query!, completionHandler: {
            (ticket: GTLServiceTicket?, object: Any?, error: Error?) -> Void in
            if error != nil {
                for handler in self.onFailure {
                    handler(ticket, error as Optional<NSError>)
                }
            } else {
                for handler in self.onSuccess {
                    handler(ticket, object as Optional<AnyObject>)
                }
            }
        })
    }
    return ticket
}

2.

func sendRequest() -> GTLServiceTicket? {
    if self.query != nil && shouldSend {
        self.ticket = appService.executeQuery(query!) { ticket, object, error in
            if error != nil {
                for handler in self.onFailure {
                    handler(ticket, error as Optional<NSError>)
                }
            } else {
                for handler in self.onSuccess {
                    handler(ticket, object as Optional<AnyObject>)
                }
            }
        }
    }
    return ticket
}