从视图控制器分离的文件中呈现视图控制器

Question

我有一个应用程序，它利用Alamofire向后端发送请求，后端会吐出响应，根据响应，应用程序会预成型一个操作。我发现Alamofire代码对于我的项目来说太乱了，我想把代码解析成一行代码。为此，我将Alamofire代码块放在一个自定义框架库中名为Requests的类中。每次我从后端收到响应时，我都想运行一个函数(不是问题(，然后对下一个视图控制器执行segue/present/push(问题(。

假设我有一个Request类，它包含一个login((函数，该函数接受用户名和密码参数。调用此函数时的单行代码如下：Request.login(username, password)，最终为Request.logout()等。此函数可以在同一Xcode项目中的ACommonLibrary框架中找到。这将运行Alamofire代码来发送请求，然后获得JSON格式的"authenticated:true"响应，根据该响应，应用程序将segue/present/push发送到Profile视图控制器。

我试着用一个布尔值来做这件事，如果我得到一个响应，一个变量将从false设置为true，并由函数返回，这样我就可以在if/else语句中使用它，但这不起作用。我用正常试用

let storyboard:UIStoryboard = UIStoryboard(name: "login", bundle: nil)
let vc = storyboard.instantiateViewController(withIdentifier: "Login") as! LoginViewController
self.present(vc, animated: true, completion: nil)

但我得到实例成员"present"不能用于类型"Request"然后我发现有人问如何从分离的视图控制器中呈现视图控制器？但这也不起作用，假设这是因为我在一个故事板中有多个视图控制器。

我搜索了这个错误和其他类似的错误，但都没有结果。所以现在我在质疑这是否有可能实现，或者我必须以不同的方式来对待它？任何建议都将不胜感激。提前谢谢。

编辑：添加了以下代码。

主
->登录
->LoginViewController.swift

class LoginViewController: UIViewController {
@IBOutlet weak var usernameTextField: CustomTextField!
@IBOutlet weak var passwordTextField: CustomTextField!
@IBOutlet weak var loginButton: UIButton!
@IBOutlet weak var forgotPasswordButton: UIButton!
@IBOutlet weak var navigationBar: UINavigationBar!
override func viewWillAppear(_ animated: Bool) {
UIApplication.shared.statusBarStyle = .lightContent
}
override func viewDidLoad() {
super.viewDidLoad()
}
// MARK: - IBActions
@IBAction func loginPressed(sender: AnyObject) {
usernameTextField.trimSpaces()
let username = usernameTextField.text!
let password = passwordTextField.text!
Request.login(username, password)
}
}

ACommonLibrary
->后端
->Request.swift

public class Request {
public class func login(_ username:String, _ password:String) {
let headers: HTTPHeaders = [
"Content-Type": "application/x-www-form-urlencoded"
]
let parameters:Parameters = [
"username": username,
"password": password
]
let endpoint = GlobalVariables.BaseURLString + "login"
Alamofire.request(endpoint, method: .post, parameters: parameters, headers: headers)
.responseJSON { response in
switch response.result {
case .success/*(let data)*/:
if response.result.value != nil{
let swiftyJsonVar = JSON(response.result.value!)
let responseSuccess = swiftyJsonVar["success"]
let responseMessage = swiftyJsonVar["error_message"]
let responseSession = swiftyJsonVar["session_id"]
let responseUserId = swiftyJsonVar["user_id"]
if responseSession != JSON.null {
GlobalVariables.Keychain["user_id"] = responseUserId.rawValue as? String
GlobalVariables.Keychain["session_id"] =  responseSession.rawValue as? String
try? GlobalVariables.Keychain.set(username, key: "username")
if responseSuccess.boolValue {
let storyboard:UIStoryboard = UIStoryboard(name: "profile", bundle: nil)
let vc = storyboard.instantiateViewController(withIdentifier: "ProfileNavigation") as!     ProfileViewController
self.present(vc, animated: true, completion: nil)
}else{
SCLAlertView().showNotice("Warning!", subTitle: responseMessage.stringValue)
}
}else{
SCLAlertView().showError("Error logging in", subTitle: "There was an error while logging in     to your account. If this error persists, the server is down :D ")
}
}
case .failure/*(let err)*/:
//          NSLog("------------------DATA START-------------------")
//          NSLog("Response String: (String(describing: err))")
SCLAlertView().showError("Error logging in", subTitle: "There was an error while logging in to     your account. If this error persists, the server is down :D ")
//          NSLog("------------------DATA END-------------------")
}
}
}    

Answer 1

首先，您应该知道self在类方法中是不可访问的，而您试图在Requests类的login方法中这样做。你想做的事情有两种可能，如下所述。

1. Requests不是UIViewController的一个子类。只有UIViewController或其子类才能呈现另一个视图控制器。所以可以使用共享应用程序的keyWindow和rootViewController。方法如下：

   if responseSuccess.boolValue {
   let storyboard:UIStoryboard = UIStoryboard(name: "profile", bundle: nil)
   let vc = storyboard.instantiateViewController(withIdentifier: "ProfileNavigation") as! ProfileViewController
   let rootVC = UIApplication.shared.keyWindow?.rootViewController
   rootVC?.present(vc, animated: true, completion: nil)
   } else {
   SCLAlertView().showNotice("Warning!", subTitle: responseMessage.stringValue)
   }
   

2. 在进行异步网络调用的方法中使用闭包，就像在login方法中一样。然后执行segues并在闭包中显示/呈现视图控制器。方法如下：

   public class Request {
   public class func login(_ username:String, _ password:String, withSuccess successHandler:@escaping (Bool) -> Void, andFailure failureHandler:@escaping (String) -> Void) {
   let headers: HTTPHeaders = ["Content-Type": "application/x-www-form-urlencoded"]
   let parameters:Parameters = ["username": username, "password": password]
   let endpoint = GlobalVariables.BaseURLString + "login"
   Alamofire.request(endpoint, method: .post, parameters: parameters, headers: headers)
   .responseJSON { response in
   switch response.result {
   case .success/*(let data)*/:
   if response.result.value != nil{
   let swiftyJsonVar = JSON(response.result.value!)
   let responseSuccess = swiftyJsonVar["success"]
   let responseMessage = swiftyJsonVar["error_message"]
   let responseSession = swiftyJsonVar["session_id"]
   let responseUserId = swiftyJsonVar["user_id"]
   if responseSession != JSON.null {
   GlobalVariables.Keychain["user_id"] = responseUserId.rawValue as? String
   GlobalVariables.Keychain["session_id"] =  responseSession.rawValue as? String
   try? GlobalVariables.Keychain.set(username, key: "username")
   if responseSuccess.boolValue {
   successHandler(true)
   } else {
   failureHandler(responseMessage.stringValue)
   }
   } else {
   failureHandler("There was an error while logging in to your account. If this error persists, the server is down :D")
   }
   }
   case .failure/*(let err)*/:
   failureHandler("There was an error while logging in to your account. If this error persists, the server is down :D")
   }
   }
   }
   }
   

   然后在LoginViewController中

   @IBAction func loginPressed(sender: AnyObject) {
   usernameTextField.trimSpaces()
   let username = usernameTextField.text!
   let password = passwordTextField.text!
   Request.login(username,
   password,
   withSuccess: { (success) in
   let vc = self.storyboard?.instantiateViewController(withIdentifier: "ProfileViewController") as! ProfileViewController
   self.present(vc, animated: true, completion: nil)
   }) { (errorMsg) in
   SCLAlertView().showError("Error logging in", subTitle: errorMsg)
   }
   }