Question

当我试图运行int（编码器:)它显示此错误时，我不知道为什么？＆＃34;不可用的初始化程序要求init（编码器:)无法通过可用的初始化程序来满足（＆＃39; init？＆＃39;）＆＃34;

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，顺便说一下，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，即初始化（编码器:)＆＃39;方法无法实现，所以我所做的就是覆盖＆＃39; init（）＆＃39; “初始化”（编码器：）＆＃39;方法，因为它需要调用＆＃39; self.init（）＆＃39;。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
}
}

我制作了＆＃39; init（）＆＃39;方法private，这样只有类中的方法才能调用它。我还必须打开评级，因为应用程序崩溃抱怨无法使用ratingKey取消归档Int。

Answer 2

关于细节的猜测，但是，一般来说 - Swift的精确语法和语义在Xcode 6（比如Xcode 6.4）和新的Xcode 7 beta之间发生了显着的变化。 Xcode 6.4支持/使用Swift语言版本1.2; Xcode 7使用Swift语言版本2.0（beta）

Answer 3

找到一个在xcode6上运行上面代码的解决方案，应该从init（编码器aDecoder）中删除“方便”并使用super.init（）而不是self.init（名称：name，photo：photo，rating：rating）然后它完美地运作

class Note: NSObject, NSCoding {

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

    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.

    }

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



    required init(coder aDecoder: NSCoder) {
        self.name = aDecoder.decodeObjectForKey(PropertyKey.nameKey) as! String

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

        self.rating = aDecoder.decodeIntegerForKey(PropertyKey.ratingKey) as Int

        // Must call designated initializer.
        super.init()
    }



  }

显示错误非失败的初始化程序＆＃34; init（编码器:)＆＃34;错误

3 个答案: