雨燕2.1：獲取錯誤而延長NSObject的

Question

我創造了示例應用程序用於測試failable初始化。當我伸出NSObject的，然後我得到下面的錯誤。

1）屬性'self.userName'未在super.init調用時初始化。
2） 不可變值「self.userDetails」可以僅進行一次初始化。
3） 不可變值「self.userName」可以僅進行一次初始化。

請找到下面的代碼和屏幕截圖是相同的。

class User: NSObject { 

    let userName: String! 
    let userDetails: [String]? 

    init?(dictionary: NSDictionary) { 
     super.init() 

     if let value = dictionary["user_name"] as? String { 
      self.userName = value 
     } 
     else { 
      return nil 
     } 

     self.userDetails = dictionary["user_Details"] as? Array 
    }   
} 

截圖

Answer 1

所有屬性必須初始化之前super.init()

無必須從failable初始化器super.init()後返還。這種限制should be removed in Swift 2.2

正確的執行將是：

class User: NSObject { 

    let userName: String! 
    let userDetails: [String]? 

    init?(dictionary: NSDictionary) { 
     if let value = dictionary["user_name"] as? String { 
      self.userName = value 
     } else { 
      self.userName = nil 
     } 

     self.userDetails = dictionary["user_Details"] as? Array 

     super.init() 

     if userName == nil { 
      return nil 
     } 

     else if userDetails == nil { 
      return nil 
     } 
    } 
} 

Answer 2

import Foundation 

let dictionary = ["user_name": "user", "user_Details":[1,2,3]] 

class User: NSObject { 

    var userName: String? 
    var userDetails: [String]? 

    init?(dictionary: NSDictionary) { 
     super.init() 
     if let value = dictionary["user_name"] as? String { 
      self.userName = value 
     } 
     else { 
      return nil 
     } 

     self.userDetails = dictionary["user_Details"] as? Array 
    }   
} 

let c = User(dictionary: dictionary) 
dump(c) 
/* 
▿ User 
    ▿ Some: User #0 
    - super: <__lldb_expr_31.User: 0x7fe372f15860> 
    ▿ userName: user 
     - Some: user 
    - userDetails: nil 
*/