ios - 显示错误不可失败初始化程序 "init(coder:)"错误

Question

当我尝试运行 int(coder:) 时它显示此错误，我不知道为什么？ “不可失败的初始化器要求 init(coder:) 不能被可失败的初始化器 ('init?') 满足”

class Note: NSObject, NSCoding {

    var name: String
    var photo: UIImage?
    var rating: Int

    static let DocumentsDirectory: AnyObject = NSFileManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).first!
    static let ArchiveURL = DocumentsDirectory.URLByAppendingPathComponent("notes")

    struct PropertyKey {
    static let nameKey = "name"
    static let photoKey = "photo"
    static let ratingKey = "rating"
     }


    init?(name: String, photo: UIImage?, rating: Int) {

    self.name = name
    self.photo = photo
    self.rating = rating

    super.init()

    // Initialization should fail if there is no name or if the rating is negative.
    if name.isEmpty || rating < 0 {
        return nil
        }

    }

    func encodeWithCoder(aCoder: NSCoder) {
    aCoder.encodeObject(name, forKey: PropertyKey.nameKey)
    aCoder.encodeObject(photo, forKey: PropertyKey.photoKey)
    aCoder.encodeInteger(rating, forKey: PropertyKey.ratingKey)
    }

    required convenience init?(coder aDecoder: NSCoder) {

    let name = aDecoder.decodeObjectForKey(PropertyKey.nameKey) as! String

    // Because photo is an optional property of Meal, use conditional cast.
    let photo = aDecoder.decodeObjectForKey(PropertyKey.photoKey) as? UIImage

    let rating = aDecoder.decodeIntegerForKey(PropertyKey.ratingKey)

    // Must call designated initializer.
    self.init(name: name, photo: photo, rating: rating)

    }


}

我正在使用 xcode 6，顺便说一句，当这段代码在 xcode 7 中运行时，它没有显示任何错误，原因是什么？

Answer 1

所以我找到了一种让它工作的方法，“init(coder:)”方法不能失败，所以我所做的就是重写“init(coder:)”调用的“init()”方法)' 方法，因为它需要调用 'self.init()'。所以这是代码:

class Meal: NSObject, NSCoding {

// MARK: Archiving Paths
static let DocumentsDirectory   = NSFileManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).first!
static let ArchiveURL           = DocumentsDirectory.URLByAppendingPathComponent("meals")

// MARK: Properties
var name:   String
var rating: Int
var photo:  UIImage?

// MARK: Types
struct PropertyKey {
    static let nameKey      = "name"
    static let photoKey     = "photo"
    static let ratingKey    = "rating"
}

// MARK: Initialization

init? (name: String, rating: Int, photo: UIImage?) {
    // Intialize stored properties.
    self.name   = name
    self.rating = rating
    self.photo  = photo

    super.init()

    // Initialization should fail if there is no name or if the rating is negative.
    if self.name.isEmpty || (rating < 0) {
        return nil
    }
}

override private init () {
    self.name   = ""
    self.rating = 0
    self.photo  = nil
}

// MARK: NSCoding

func encodeWithCoder(aCoder: NSCoder) {
    aCoder.encodeObject(self.name, forKey: PropertyKey.nameKey)
    aCoder.encodeObject(self.photo, forKey: PropertyKey.photoKey)
    aCoder.encodeObject(self.rating, forKey: PropertyKey.ratingKey)
}

convenience required init(coder aDecoder: NSCoder) {
    self.init()

    let name    = aDecoder.decodeObjectForKey(PropertyKey.nameKey) as! String
    if let rating  = aDecoder.decodeIntegerForKey(PropertyKey.ratingKey) {
        self.rating = rating
    }

    // Because photo is an optional property of Meal, use conditional cast.
    let photo   = aDecoder.decodeObjectForKey(PropertyKey.photoKey) as? UIImage

    self.name   = name
    self.photo  = photo
}
}

我将“init()”方法设为私有(private)，这样只有类内部的方法才能调用它。我还必须选择解包评级，因为应用程序崩溃并提示无法使用 ratingKey 取消存档 Int。