Question

我正在使用具有登录屏幕的应用程序，这对我来说是第一次。在关注了为此提供教程的不同网站之后，我创建了一个LoginService ViewController，它将有助于登录该应用程序。

以下是我在此ViewController中使用的代码的一部分：

 // MARK: Private Methods

private func exchangeTokenForUserAccessTokenWithCompletionHandler(username: String, password: String, completion: (OAuthInfo?, error: String?) -> ()) {

    let path = "/oauthfake/token/"
    let url = ConnectionSettings.apiURLWithPathComponents(path)
    let request = NSMutableURLRequest(URL: url)
    request.HTTPMethod = "POST"

    var params =  "client_id=\(ConnectionSettings.clientId)&client_secret=\(ConnectionSettings.clientSecret)&grant_type=password&login=\(username)&password=\(password)"

    var err: NSError?
    request.HTTPBody = params.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)
    request.addValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")


    let task = session.dataTaskWithRequest(request) {data, response, error -> Void in

        var err: NSError?
        var json = NSJSONSerialization.JSONObjectWithData(data, options: .MutableLeaves, error: &err) as? NSDictionary

        if (err != nil) {

            // Something went wrong, log the error to the console.
            print(err!.localizedDescription)
            let jsonStr = NSString(data: data!, encoding: NSUTF8StringEncoding)
            print("Something went wrong: '\(jsonStr)")

            completion(nil, error: err?.localizedDescription)
        } else {
            if let parseJSON = json {
                if let token = parseJSON.valueForKey("access_token") as? String {
                    if var issuedAt = parseJSON.valueForKey("issued_at") as? String {
                        if var tokenExpiresIn = parseJSON.valueForKey("expires_in") as? String {
                            if var refreshTokenIssuedAt = parseJSON.valueForKey("refresh_token_issued_at") as? String {
                                if let refreshToken = parseJSON.valueForKey("refresh_token") as? String {
                                    if var refreshTokenExpiresIn = parseJSON.valueForKey("refresh_token_expires_in") as? String {
                                        if let refreshCount = parseJSON.valueForKey("refresh_count") as? String {

                                            let epochIssuedAt:Double = (issuedAt as NSString).doubleValue / 1000.0
                                            let epochRefreshTokenIssuedAt:Double = (refreshTokenIssuedAt as NSString).doubleValue / 1000.0

                                            let oauthInfo = OAuthInfo(issuedAt: epochIssuedAt, refreshTokenIssuedAt: epochRefreshTokenIssuedAt, tokenExpiresIn: (tokenExpiresIn as NSString).doubleValue, refreshToken: refreshToken, token: token, refreshTokenExpiresIn: (refreshTokenExpiresIn as NSString).doubleValue, refreshCount: (refreshCount as NSString).integerValue)

                                            completion(oauthInfo, error: err?.localizedDescription)

我的super.init似乎运行正常（上面没有特色），以及此文件中的其余代码，但我得到一个错误，阅读＆＃34;额外的参数＆＃39;错误＆＃39;在电话＆＃34;在这一行：

var json = NSJSONSerialization.JSONObjectWithData(data, options: .MutableLeaves, error: &err) as? NSDictionary

我已经知道Swift 2.0处理的错误与我以前的错误不同。我知道这个版本的Swift使用try，let和catch代码来处理错误。我的问题是我之前没有使用过这些类型的代码，也不确定如何在这种情况下使用它们。

Answer 1

在iOS 7和后者NSJSONSerialization是线程安全的。现在你可以使用do try catch

斯威夫特3：

do{
let JsonDict = try JSONSerialization.jsonObject(with: data, options:.MutableLeaves)
}
catch let error as NSError {
    print(error)
}

Swift 2：

do{
  let jsonDict = try NSJSONSerialization.JSONObjectWithData(data, options: .MutableLeaves) as! [String:AnyObject]
}catch let error as NSError{
  print(error)
}

Answer 2

JSONObjectWithData函数需要您提到的do try catch语法，因为其声明网站上的方法标有throws关键字。（此处有文档：https://developer.apple.com/reference/foundation/jsonserialization/1418059-jsonobject）

不要简单地使用它。

do {
try someMethodWhichCanThrow()
catch(error) {
// maybe log the error here
}

这在Swift编程语言书中有所描述：https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/ErrorHandling.html#//apple_ref/doc/uid/TP40014097-CH42-ID508

Xcode - Swift 2.0：＆＃34;额外的参数＆＃39;错误＆＃39;在电话＆＃34;与NSJSONSerialization

2 个答案: