Convert bytes/UInt8 array to Int in Swift

There are two problems:

• Int is a 64-bit integer on 64-bit platforms, your input datahas only 32-bit.
• Int uses a little-endian representation on all current Swift platforms,your input is big-endian.

That being said the following would work:

let array : [UInt8] = [0, 0, 0, 0x0E]var value : UInt32 = 0let data = NSData(bytes: array, length: 4)data.getBytes(&value, length: 4)value = UInt32(bigEndian: value)print(value) // 14

Or using Data in Swift 3:

let array : [UInt8] = [0, 0, 0, 0x0E]let data = Data(bytes: array)let value = UInt32(bigEndian: data.withUnsafeBytes { $0.pointee })

With some buffer pointer magic you can avoid the intermediatecopy to an NSData object (Swift 2):

let array : [UInt8] = [0, 0, 0, 0x0E]var value = array.withUnsafeBufferPointer({      UnsafePointer<UInt32>($0.baseAddress).memory})value = UInt32(bigEndian: value)print(value) // 14

For a Swift 3 version of this approach, see ambientlight's answer.

In Swift 3 it is now a bit more wordy:

let array : [UInt8] = [0, 0, 0, 0x0E]let bigEndianValue = array.withUnsafeBufferPointer {         ($0.baseAddress!.withMemoryRebound(to: UInt32.self, capacity: 1) { $0 })}.pointeelet value = UInt32(bigEndian: bigEndianValue)

I think Martin's answer is better than this, but I still want to post mine. Any suggestion would be really helpful.

let array : [UInt8] = [0, 0, 0, 0x0E]var value : Int = 0for byte in array {    value = value << 8    value = value | Int(byte)}print(value) // 14