Swift 3 建议更正 "cannot convert value for ' (CKAccountStatus, NSError?) -> ( )' to ' ... -> Void'

Question

我在函数的第三行收到错误无法将“(CKAccountStatus, NSError?) -> ()”的值转换为“(CKAccountStatus, NSError?) -> Void” 。

这是代码:

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    container.accountStatusWithCompletionHandler{
        (status: CKAccountStatus, error: NSError?) in
        dispatch_async(dispatch_get_main_queue(), {
            var title: String!
            var message: String!
            if error != nil{
                title = "Error"
                message = "An error occurred = \(error)"
            } else {
                //title = "No errors occurred getting info"
                switch status{
                case .Available:
                    message = "The user is logged in to iCloud"
                    title = "GOOD"
                    print("determined status was available")
                    self.shouldPullFromICloud()
                //self.displayAlertWithTitle(title, message: message)
                case .CouldNotDetermine:
                    message = "Could not determine if the user is logged" +
                    " into iCloud or not"
                    title = "BAD"
                    self.noUserIsSignedIn()
                case .NoAccount:
                    message = "User is not logged into iCloud"
                    title = "BAD"
                    self.noUserIsSignedIn()
                case .Restricted:
                    message = "Could not access user's iCloud account information"
                    title = "BAD"
                    self.noUserIsSignedIn()
                }
                print(title, message)
            }
        })
    }
}

现在 Xcode 通过在倒数第二行插入“as! (CKAccountStatus, Error?) -> Void”来提供“修复它”。这没有帮助，它只是不断询问我是否要“修复它”，如果我单击它，它只会继续添加越来越多的“as!(CKAccountStatus，Error？)-> Void”。以下是单击“修复它”按钮后的样子:

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    container.accountStatusWithCompletionHandler{
        (status: CKAccountStatus, error: NSError?) in
        dispatch_async(dispatch_get_main_queue(), {
            var title: String!
            var message: String!
            if error != nil{
                title = "Error"
                message = "An error occurred = \(error)"
            } else {
                //title = "No errors occurred getting info"
                switch status{
                case .Available:
                    message = "The user is logged in to iCloud"
                    title = "GOOD"
                    print("determined status was available")
                    self.shouldPullFromICloud()
                //self.displayAlertWithTitle(title, message: message)
                case .CouldNotDetermine:
                    message = "Could not determine if the user is logged" +
                    " into iCloud or not"
                    title = "BAD"
                    self.noUserIsSignedIn()
                case .NoAccount:
                    message = "User is not logged into iCloud"
                    title = "BAD"
                    self.noUserIsSignedIn()
                case .Restricted:
                    message = "Could not access user's iCloud account information"
                    title = "BAD"
                    self.noUserIsSignedIn()
                }
                print(title, message)
            }
        })
    } as! (CKAccountStatus, Error?) -> Void
}

Answer 1

首先两件事:

accountStatusWithCompletionHandler(_:) 在 Swift 3 中已重命名为 accountStatus(completionHandler:)。

func accountStatus(completionHandler: (CKAccountStatus, Error?) -> Void)

正如已经评论过的，completeHandler 的类型已经改变:

completionHandler: @escaping (CKAccountStatus, Error?) -> Void

当使用闭包表达式提供闭包参数时，您无需担心@escaping。

因此，您需要替换这两行:

    container.accountStatusWithCompletionHandler{
        (status: CKAccountStatus, error: NSError?) in

有了这些:

    container.accountStatus {
        (status: CKAccountStatus, error: Error?) in

您可能会在 Swift 3 中发现许多其他需要修复的部分，但是修复了上述两个部分后，Xcode 会给您更好的建议。

(在测试上面的代码之前，不要忘记删除 as! (CKAccountStatus, Error?) -> Void。)