Can't save Bool in Swift

Question

I'm new to Swift (background in C++) and I'm trying to do a very simple thing: save a Bool. It works perfectly if I convert the bool to a string that is either "A" or "B" and then convert back but if I save the bool directly with encode and aDecoder the Bool comes back nil every time. Can't find anything about it on the internet.

As you can see below I simply substitute a string for a Bool and it works.

func boolwontsave(aBool:Bool) -> String {
    if aBool {
        return "A"
    }
    return "B"
}

func encode(with aCoder: NSCoder) {

    aCoder.encode(name, forKey: PropertyKey.name)
    aCoder.encode(number, forKey: PropertyKey.number)
    aCoder.encode(boolwontsave(aBool: ispresent), forKey: PropertyKey.present)

}

required convenience init?(coder aDecoder: NSCoder) {

    // The name is required. If we cannot decode a name string, the initializer should fail.
    guard let name = aDecoder.decodeObject(forKey: PropertyKey.name) as? String else {
        os_log("Unable to decode the name for a player object.", log: OSLog.default, type: .debug)
        return nil
    }

    let number = aDecoder.decodeObject(forKey: PropertyKey.number) as? String

    guard let localpresent = aDecoder.decodeObject(forKey: PropertyKey.present) as? String else {
        print("got the nil")
        os_log("Unable to decode the ispresent for a player object.", log: OSLog.default, type: .debug)
        return nil
    }


    // Must call designated initializer.
    self.init(name:name, number:number, present: localpresent == "A")

}

Aren't Bools supposed to save? This seems inelegant.

user_10446942 · Answer

Use decodeBool(forKey key: String) instead of decodeObject(forKey: String)

DecodeBool decodes and returns a boolean value that was previously encoded with encode(_:forKey:) and associated with the string key.

aCoder.encode(true, forKey: PropertyKey.present)
aCoder.decodeBool(forKey: PropertyKey.present)

user_5044042 · Answer

It's very easy to save a Bool if you are using the proper API.

In terms of NSCoding a Bool is not an object, there is a decodeBool(forKey method.

required convenience init?(coder aDecoder: NSCoder) {

    // The name is required. If we cannot decode a name string, the initializer should fail.
    guard let name = aDecoder.decodeObject(forKey: PropertyKey.name) as? String else {
        os_log("Unable to decode the name for a player object.", log: OSLog.default, type: .debug)
        return nil
    }

    let number = aDecoder.decodeObject(forKey: PropertyKey.number) as? String
    let localpresent = aDecoder.decodeBool(forKey: PropertyKey.present)

    // Must call designated initializer.
    self.init(name:name, number:number, present: localpresent)

}

func encode(with aCoder: NSCoder) {
    aCoder.encode(name, forKey: PropertyKey.name)
    aCoder.encode(number, forKey: PropertyKey.number)
    aCoder.encode(ispresent, forKey: PropertyKey.present)
}

In Swift 4+ I'd prefer the native Codable protocol over constrained NSCoding.

NSCoding requires an class inherited from NSObject.
Codable can be used for any struct, class and enum which conforms to the protocol.

Can't save Bool in Swift

2 Answers