How to save an array of Int64 variables using NSCoding in Swift

Question

I am currently using NSCoding to save an array of Int variables like this:

var myArray = [Int]()

myArray = aDecoder.decodeObjectForKey("MyArray") as! [(Int)]

aCoder.encodeObject(myArray, forKey: "MyArray")

I now need to save an array of Int64 variables. I thought it would be simple, so I did this:

var myNewArray = [Int64]()

myNewArray = aDecoder.decodeObjectForKey("MyNewArray") as! [(Int64)]

aCoder.encodeObject(myNewArray, forKey: "MyNewArray")

However I get an error on the last line: Cannot convert value of type '[Int64]' to expected argument type 'AnyObject?'

I am puzzled as to why it works with Int but not Int64. How can I achieve this?

Have a look at How can I get an NSCoder to encode/decode a Swift array of structs? for a possible solution. — Martin R
– Martin R, Commented Sep 3, 2016 at 17:16

OOPer · Accepted Answer · 2016-09-03 15:55:58Z

1

In the current version of Swift, when you convert [Int] to AnyObject (or AnyObject?), Swift generates NSArray containing NSNumbers. Although NSNumber can contain Int64 (long long int in C/Objective-C), Swift does not convert Int64 to NSNumber automatically, thus, [Int64] cannot be automatically converted to AnyObject.

You can generate an NSArray containing NSNumber explicitly.

let myI64Array = aDecoder.decodeObjectForKey("MyNewArray") as! [NSNumber]
myNewArray = myI64Array.map{$0.longLongValue}

Or:

let myI64Array = myNewArray.map{NSNumber(longLong: $0)}
aCoder.encodeObject(myI64Array, forKey: "MyNewArray")

answered Sep 3, 2016 at 15:55

OOPer

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matt · Accepted Answer · 2016-09-03 15:50:58Z

1

I am puzzled as to why it works with Int but not Int64. How can I achieve this?

It doesn't actually work with Int either. You have to have an array of Objective-C objects, and a number is not an object in Objective-C.

However, Swift bridges Int to NSNumber automatically, so it looks like it works.

It doesn't do that for Int64. You have to create the NSNumber objects yourself.

answered Sep 3, 2016 at 15:50

matt

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