Working with bytes and strings in Swift (Unicode Scalar, UTF8 and UTF16)

Calculating a count for UTF16 string with unicode scalar characters - use utf16Count

newStr = "hello 😂😒😡"

// the number of elements:
let count = newStr.utf16Count

// create array of appropriate length:
var array = [UInt16](count: count, repeatedValue: 0)


for a in enumerate(newStr.utf16) {
array[a.index] = a.element
}


NSString(bytes: &array, length: count*sizeof(UInt16), encoding: NSUTF16LittleEndianStringEncoding)

Unicode Scalar and UInt32

var str = "Hello "
var str2 = "playground"
// create unicode scalar array
var arr = [UnicodeScalar]()
// add byte array of unicode scalars
arr += str.unicodeScalars
var arr2 = [UnicodeScalar]()
arr2 += str2.unicodeScalars
arr += arr2

var str3 = String()
// extract characters from array
for a in arr {
str3.append(Character(a))
}

str3  // returns "Hello playground"

// Alternative that works
if let b = String.stringWithBytesNoCopy(&arr, length:arr.count * sizeof(UnicodeScalar), encoding: NSUTF32LittleEndianStringEncoding,  freeWhenDone: false) {
    b
}

UTF16 and UInt16

var str = "Hello "
var str2 = "playground"
// create UInt16 array
var arr = [UInt16]()
// add byte array of UInt16
arr += str.utf16
var arr2 = [UInt16]()
arr2 += str2.utf16
arr += arr2

if let a = String.stringWithBytesNoCopy(&arr, length:arr.count * sizeof(UInt16), encoding: NSUTF16LittleEndianStringEncoding,  freeWhenDone: false) {
    a
}

UTF8 and UInt8

var str = "Hello "
var str2 = "playground"
// create UInt8 array
var arr = [UInt8]()
// add byte array of UInt8
arr += str.utf8
var arr2 = [UInt8]()
arr2 += str2.utf8
arr += arr2

if let a = String.stringWithBytes(arr, encoding:NSUTF8StringEncoding) {
    a
}

In these examples I've transformed two strings into byte arrays, concatenated the byte arrays and then transformed back into strings.