未使用单例调用委托方法

Question

已经有人问过类似的问题，但没有帮助。我正在尝试从视图控制器调用 Singleton class 中声明的协议方法，但被调用的方法从不调用。

我的协议和 class 是：

import Foundation

protocol ServiceDelegate {
  func serviceData(data: [String: Any])
}

class Service {

private static let sharedInstance = Service()  // singleton object
var delegate: ServiceDelegate?

class func shared() -> Service {
    return sharedInstance
}

func login(postData:String) {

    let url = URL(string: "MY_URL")!
    var request = URLRequest(url: url)
    request.httpMethod = "POST"
    request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
    let dataBody = postData.data(using:String.Encoding.ascii, allowLossyConversion: false)
    request.httpBody = dataBody
    let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
        guard let data = data, error == nil else {
            print(error?.localizedDescription ?? "No data")
            return
        }
        let responseJSON = try? JSONSerialization.jsonObject(with: data, options: [])
        if let dataArray = responseJSON as? [String: Any] {
            self.delegate?.serviceData(data: dataArray)   // This is getting called
        }
    }
    task.resume()
  }
}

我的视图控制器class实现协议的地方是：

import UIKit

class LoginVC: UIViewController, ServiceDelegate {

var serviceInstance: Service = Service()

override func viewDidLoad() {
    super.viewDidLoad()
    serviceInstance.delegate = self
}

@IBAction func loginBtn(_ sender: Any) {
    let info = "userName=\(String(describing: usernameText.text!))&password=\(String(describing: passwordText.text!))"
    Service.shared().login(postData: info)
}

// This is not getting called:
func serviceData(data: [String : Any]) {
    print(data)
}

以上实现是否正确？我可以使用私有单例对象来成功实现协议方法吗？

Answer 1

您正在创建两个 Service 个实例。您应该只使用 Service.shared() 返回的那个。这是在您的应用程序中共享的实际单例。

在您的视图控制器中，替换此行：

serviceInstance.delegate = self

与：

Service.shared().delegate = self

你也应该删除这一行（即不必要的第二个实例）：

var serviceInstance: Service = Service()

未使用单例调用委托方法

Delegate method not called using Singleton

singleton

delegates

protocols

swift4

ios11