如何在Swift中使用NSCoding保存Int64变量数组

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?

Answer 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.

Answer 2

In the current version of Swift, when you convert [Int] to AnyObject (or AnyObject? ), Swift generates NSArray containing NSNumber s. 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")