swift - 函数返回 Swift 后赋值

Question

我遇到了一个奇怪的错误，我的函数在返回后将一个值附加到数组...代码如下:

func makeUser(first: String, last: String, email: String) -> [User] {

    var userReturn = [User]()

    RESTEngine.sharedEngine.registerUser(email, firstName: first, lastName: last, age: 12, success: { response in
        if let response = response, result = response["resource"], id = result[0]["_id"] {

            let params: JSON =
            ["name": "\(first) \(last)",
             "id": id as! String,
             "email": email,
             "rating": 0.0,
             "nuMatches": 0,
             "nuItemsSold": 0,
             "nuItemsBought": 0]
             let user = User(json: params)

            userReturn.append(user)
            print("\(userReturn)")

        }
        }, failure: { error in
            print ("Error creating a user on the server: \(error)")
    })

    return userReturn
}

我从这里调用 make user:

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    var newUser = makeUser("Average", last: "Person", email: "a.Person@mail.com")
    print("\(newUser)")
}

(这一切仍在测试中，所以我显然在奇怪的地方调用了我的代码。)

所以当我运行这个时，最终发生的是首先打印我的“newUser”数组(它显示为空)，然后打印我在 makeUser 函数中本地分配的 userReturn 数组，它包含新的我在“registerUser”的“成功”完成 block 中附加到它的用户，如下所示:

有谁知道这里发生了什么，我该如何解决？

供引用:JSON 只是我为 [String: AnyObject] 字典定义的类型别名。

Answer 1

registerUser 异步运行，因此您应该应用异步模式，例如完成处理程序:

func makeUser(first: String, last: String, email: String, completionHandler: ([User]?, ErrorType?) -> ()) {
    RESTEngine.sharedEngine.registerUser(email, firstName: first, lastName: last, age: 12, success: { response in
        if let response = response, result = response["resource"], id = result[0]["_id"] {
            var users = [User]()

            let params: JSON =
            ["name": "\(first) \(last)",
             "id": id as! String,
             "email": email,
             "rating": 0.0,
             "nuMatches": 0,
             "nuItemsSold": 0,
             "nuItemsBought": 0]
            let user = User(json: params)
            users.append(user)

            completionHandler(users, nil)
        } else {
            let jsonError = ...  // build your own ErrorType or NSError indicating that the the parsing of the JSON failed for some reason
            completionHandler(nil, jsonError)
        }
    }, failure: { error in
        completionHandler(nil, error)
    })
}

然后像这样使用它:

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    makeUser("Average", last: "Person", email: "a.Person@mail.com") { users, error in
        guard error == nil else {
            print(error)
            return
        }

        print("\(users)")
        // if you're doing anything with this, use it here, e.g. reloadTable or update UI controls
    }

    // but don't try to use `users` here, as the above runs asynchronously
}