函数在返回Swift后赋值 [英] Function assigning values after it returns Swift

问题描述

我遇到一个奇怪的错误，其中我的函数在数组返回后附加一个值...这段代码如下：

I'm running into a weird bug where my function appends a value to an array AFTER it returns... The code for this is below :

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用户：

I call make user from here:

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

（这仍然是测试，所以我显然调用我的代码在奇怪的地方。）

(This is all still testing so I'm obviously calling my code in weird places.)

所以当我运行这个最终发生的是，我的newUser数组被打印（它显示为空），然后我的本地分配的userReturn数组makeUser函数打印，它包含我在registerUser的成功完成块中附加的新用户，如下所示：

So when I run this what ends up happening is that FIRST my "newUser" array gets printed (and it shows up empty), and afterwards the userReturn array that I assign locally within the makeUser function prints, and it contains the new user that I append to it within the "success" completion block of "registerUser", like so:

有人知道这里发生了什么，以及如何解决这个问题？

Does anyone know whats happening here, and how I could fix it?

参考：JSON只是一个typealias为[String：AnyObject]字典定义。

For reference: JSON is simply a typealias I defined for [String: AnyObject] dictionary.

推荐答案

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

The registerUser runs asynchronously, so you should apply asynchronous pattern, such as completion handler:

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)
    })
}

并使用它：

override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view, typically from a nib.
    makeUser("Average", last: "Person", email: "[e-mail]") { 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
}

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