Swift: Does not conform to protocol NSCoding

Question

I am trying to use the NSCoding protocol on a class I have written in swift, but cannot seem to figure out why the compiler complains that it \"does not conform to protocol

Answer 1

As you can see in the detailed compiler messages in the Report navigator, your methods are not declared correctly:

error: type 'ServerInfo' does not conform to protocol 'NSCoding'
class ServerInfo: NSObject, NSCoding {
^
Foundation.NSCoding:2:32: note: protocol requires function 'encodeWithCoder' with type '(NSCoder) -> Void'
  @objc(encodeWithCoder:) func encodeWithCoder(aCoder: NSCoder)
                               ^
note: candidate has non-matching type '(NSCoder!) -> ()'
    func encodeWithCoder(_aCoder: NSCoder!) {
         ^
Foundation.NSCoding:3:25: note: protocol requires initializer 'init(coder:)' with type '(coder: NSCoder)'
  @objc(initWithCoder:) init(coder aDecoder: NSCoder)
                        ^
note: candidate has non-matching type '(coder: NSCoder!)'
    init(coder aDecoder: NSCoder!) {

(This may have changed between the beta releases.) In addition, the initWithCoder method has to be marked as required:

required init(coder aDecoder: NSCoder) {   }

func encodeWithCoder(_aCoder: NSCoder) {   }

In Swift 3 the required methods are

required init(coder aDecoder: NSCoder) {   }

func encode(with aCoder: NSCoder) {   }

Answer 2

The parameters are not implicitly unwrapped (remove the !), and the initializer requires the required modifier:

required init(coder aDecoder: NSCoder) {
...
func encodeWithCoder(_aCoder: NSCoder) {

For Swift 3

A minor but important change has been commited . The init method is same but the encodeWithCoder method has been modified.

   required init(coder aDecoder: NSCoder) {
    ...
   }

   func encode(with _aCoder: NSCoder) { 
   ...
   }

Answer 3

For Swift 3 (on Xcode 8.2 beta (8C23))

It appears to have changed again. This is the only variation that I could get to work...

func encodeWithCoder(_ _aCoder: NSCoder) {
    ...
}