user1256821 - 9 months ago 100

Objective-C Question

How to convert swift's

`Int64`

`UUID`

`UUID`

I can construct

`UUID`

`uuid_t`

`UInt8`

`Int64`

Is there a better way?

Answer Source

The "simplest" way to do it (without relying on the memory layout of `CollectionType`

, `Tuple`

, `UUID`

or `NSUUID`

) is:

```
extension UUID {
init(number: Int64) {
var number = number
let numberData = Data(bytes: &number, count: MemoryLayout<Int64>.size)
let bytes = [UInt8](numberData)
let tuple: uuid_t = (0, 0, 0, 0, 0, 0, 0, 0,
bytes[0], bytes[1], bytes[2], bytes[3],
bytes[4], bytes[5], bytes[6], bytes[7])
self.init(uuid: tuple)
}
var intValue: Int64? {
let tuple = self.uuid
guard tuple.0 == 0 && tuple.1 == 0 && tuple.2 == 0 && tuple.3 == 0 &&
tuple.4 == 0 && tuple.5 == 0 && tuple.6 == 0 && tuple.7 == 0 else {
return nil
}
let bytes: [UInt8] = [tuple.8, tuple.9, tuple.10, tuple.11,
tuple.12, tuple.13, tuple.14, tuple.15]
let numberData = Data(bytes: bytes)
let number = numberData.withUnsafeBytes { $0.pointee } as Int64
return number
}
}
```

Also, you may want to `throw`

/`fatalError`

instead of returning `nil`

.

`UUID`

sFor completion sake (and to make it actually possible to create valid UUIDs) I added a way to create it from 2 `Int64`

and rewrote the answer to your question using that:

`UUID`

creation from `(Int64, Int64)`

```
extension UUID {
init(numbers: (Int64, Int64)) {
var firstNumber = numbers.0
var secondNumber = numbers.1
let firstData = Data(bytes: &firstNumber, count: MemoryLayout<Int64>.size)
let secondData = Data(bytes: &secondNumber, count: MemoryLayout<Int64>.size)
let bytes = [UInt8](firstData) + [UInt8](secondData)
let tuple: uuid_t = (bytes[0], bytes[1], bytes[2], bytes[3],
bytes[4], bytes[5], bytes[6], bytes[7],
bytes[8], bytes[9], bytes[10], bytes[11],
bytes[12], bytes[13], bytes[14], bytes[15])
self.init(uuid: tuple)
}
var intTupleValue: (Int64, Int64) {
let tuple = self.uuid
let firstBytes: [UInt8] = [tuple.0, tuple.1, tuple.2, tuple.3,
tuple.4, tuple.5, tuple.6, tuple.7]
let secondBytes: [UInt8] = [tuple.8, tuple.9, tuple.10, tuple.11,
tuple.12, tuple.13, tuple.14, tuple.15]
let firstData = Data(bytes: firstBytes)
let secondData = Data(bytes: secondBytes)
let first = firstData.withUnsafeBytes { $0.pointee } as Int64
let second = secondData.withUnsafeBytes { $0.pointee } as Int64
return (first, second)
}
}
```

`UUID`

creation from `Int64`

(filling MSBs with 0s)```
extension UUID {
init(number: Int64) {
self.init(numbers: (0, number))
}
var intValue: Int64? {
let (first, second) = intTupleValue
guard first == 0 else { return nil }
return second
}
}
```