Fail to decode Int with NSCoder in Swift

Question

I am using Xcode8 Beta with Swift 3.0. I tried to encode a simple object base on NSObject, but I cannot decode Int or NSInteger type. (The encoding process is OK)

codes

class Model : NSObject, NSCoding {
    var seq: NSNumber?
    var seq2: Int? // problem with seq2, NSInteger is not ok, either
    var id: String?
    var value: String?

    override init() {
        super.init()
    }

    required init?(coder aDecoder: NSCoder){
        self.seq = aDecoder.decodeObject(forKey: "seq") as? NSNumber
        self.seq2 = aDecoder.decodeInteger(forKey: "seq2")
        self.id = aDecoder.decodeObject(forKey: "id") as? String
        self.value = aDecoder.decodeObject(forKey: "value") as? String
    }

    func encode(with aCoder: NSCoder){
        aCoder.encode(seq, forKey: "seq")
        aCoder.encode(seq2, forKey: "seq2")
        aCoder.encode(id, forKey: "id")
        aCoder.encode(value, forKey: "value")
    }
}

Rob · Accepted Answer · 2016-06-28 10:12:05Z

16

The problem is that seq2 is not an Int, but rather a Int? optional. It cannot be represented as an Objective-C integer.

You can use decodeObject:

required init?(coder aDecoder: NSCoder){
    self.seq = aDecoder.decodeObject(forKey: "seq") as? NSNumber
    self.seq2 = aDecoder.decodeObject(forKey: "seq2") as? Int
    self.id = aDecoder.decodeObject(forKey: "id") as? String
    self.value = aDecoder.decodeObject(forKey: "value") as? String

    super.init()
}

or change it so it is not optional:

class Model : NSObject, NSCoding {
    var seq: NSNumber?
    var seq2: Int
    var id: String?
    var value: String?

    init(seq: NSNumber, seq2: Int, id: String, value: String) {
        self.seq = seq
        self.seq2 = seq2
        self.id = id
        self.value = value

        super.init()
    }

    required init?(coder aDecoder: NSCoder) {
        self.seq = aDecoder.decodeObject(forKey: "seq") as? NSNumber
        self.seq2 = aDecoder.decodeInteger(forKey: "seq2")
        self.id = aDecoder.decodeObject(forKey: "id") as? String
        self.value = aDecoder.decodeObject(forKey: "value") as? String

        super.init()
    }

    func encode(with aCoder: NSCoder) {
        aCoder.encode(seq, forKey: "seq")
        aCoder.encode(seq2, forKey: "seq2")
        aCoder.encode(id, forKey: "id")
        aCoder.encode(value, forKey: "value")
    }

    override var description: String { return "<Model; seq=\(seq); seq2=\(seq2); id=\(id); value=\(value)>" }
}

edited Jun 28, 2016 at 10:12

answered Jun 28, 2016 at 10:02

Rob

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2 Comments

Crashalot Over a year ago

What's the safe way to decode values in Swift 3? For instance to guard against the scenario where you use decodeInteger and seq2 is not an Integer. This was handled in Swift 2 by using a let statement for decodeObject, but decodeInteger does not return an optional.

idrougge Over a year ago

aDecoder.containsValue(forKey:) will at least check if there is some kind of value for a given key.

Alessandro Ornano · Accepted Answer · 2016-09-23 22:20:55Z

1

Use the encodeInteger method to encode integers instead:

func encode(with aCoder: NSCoder) {
    ...
    aCoder.encodeInteger(seq2, forKey: "seq2")
}

edited Sep 23, 2016 at 22:20

answered Jun 28, 2016 at 9:54

Alessandro Ornano

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1 Comment

Crashalot Over a year ago

What's the safe way to decode values in Swift 3? For instance to guard against the scenario where you use decodeInteger and seq2 is not an Integer. This was handled in Swift 2 by using a let statement for decodeObject, but decodeInteger does not return an optional.

Adolfo · Accepted Answer · 2016-06-28 09:54:17Z

0

Take care with nil values

func encode(with aCoder: NSCoder){
    aCoder.encode(seq, forKey: "seq")

    if let second_seq = self.seq2
    {
        aCoder.encode(second_seq, forKey: "seq2")
    }
    aCoder.encode(id, forKey: "id")
    aCoder.encode(value, forKey: "value")
}

seq2 will be nil if the key is not present on decode operations

answered Jun 28, 2016 at 9:54

Adolfo

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