Converting NSData to Integer in Swift

Question

In Objective-C the code looked liked this and worked flawlessly,

NSInteger random = arc4random_uniform(99) + 1 
NSData *data = [NSData dataWithBytes:& ra         


        

Answer 1

You can extend Data type, create a generic method, get the bytes and cast it or set the resulting type explicitly as needed:

extension Data {
    func object(at index: Index = 0) -> T {
        subdata(in: index...size))
        .withUnsafeBytes { $0.load(as: T.self) }
    }
}

---

extension Numeric {
    var data: Data {
        var source = self
        return Data(bytes: &source, count: MemoryLayout.size)
    }
}

---

let data = Data([0xFF, 0x1F])   // 2 bytes

let uint16: UInt16 = data.object()      // 8191  littleEndian
let number1 = uint16.littleEndian       // 8191
let number2 = uint16.bigEndian          // 65311

let int16 = data.object() as Int16      // 8191   littleEndian
let number3 = int16.littleEndian        // 8191
let number4 = int16.bigEndian           // -225

print(number1) // 8191
print(number2) // 65311
print(number3) // 8191
print(number4) // -225

---

Testing with Int

let random = Int.random(in: 1...100)    // 15 UInt32
let data = random.data                  // 8 bytes  [15, 0, 0, 0, 0, 0, 0, 0]

Testing with UInt32

let random = UInt32.random(in: 1...100)  // 90 UInt32
let data = random.data                   // 4 bytes  [90, 0, 0, 0]

Testing with Double

let random = Double.random(in: 0...1)  // 0.2463145485351322 Double
let data = random.data                 // 8 bytes  [12, 99, 62, 49, 60, 135, 207, 63]

If you want to extract a subdata:

let data = Data([0xFF, 0x1F, 0x1F, 0xFF])      // 4 bytes

let uint16: UInt16 = data.object(at: 2)        //  65311 littleEndian
let number1 = uint16.littleEndian              // 65311
let number2 = uint16.bigEndian                 // 8191

let int16: Int16 = data.object(at: 2)          // -225   littleEndian
let number3 = int16.littleEndian               // -225
let number4 = int16.bigEndian                  // 8191

number1 // 65311
number2 // 8191
number3 // -225
number4 // 8191