I have an array of UInt32 values. I would like to convert this array to a String.
This doesn't work:
let myUInt32Array: [UInt32] = [72, 101, 108, 108, 111, 128049]
let myString = String(myUInt32Array) // error
let myString = String(stringInterpolationSegment: myUInt32Array) // [72, 101, 108, 108, 111, 128049] (not what I want)
These SO posts show UTF8 and UTF16:
UnicodeScalar is a type alias for UInt32. So cast your UInt32 values to UnicodeScalar and then append them to a String.
let myUInt32Array: [UInt32] = [72, 101, 108, 108, 111, 128049]
var myString: String = ""
for value in myUInt32Array {
if let scalar = UnicodeScalar(value) {
myString.append(Character(scalar))
}
}
print(myString) // Hello🐱
Character first, the UInt32 value must also be checked for nil.(The answer has been updated for Swift 4 and later.)
Using the Swift type Data and String this can be done as
let myUInt32Array: [UInt32] = [72, 101, 108, 108, 111, 128049, 127465, 127466]
let data = Data(bytes: myUInt32Array, count: myUInt32Array.count * MemoryLayout<UInt32>.stride)
let myString = String(data: data, encoding: .utf32LittleEndian)!
print(myString) // Hello🐱🇩🇪
A forced unwrap is used here because a conversion from UTF-32 code points to a string cannot fail.
You can define a String extension for your convenience
extension String {
init(utf32chars:[UInt32]) {
let data = Data(bytes: utf32chars, count: utf32chars.count * MemoryLayout<UInt32>.stride)
self = String(data: data, encoding: .utf32LittleEndian)!
}
}
and use it as
let myUInt32Array: [UInt32] = [72, 101, 108, 108, 111, 128049, 127465, 127466]
let myString = String(utf32chars: myUInt32Array)
print(myString) // Hello🐱🇩🇪
And just for completeness, the generic converter from https://stackoverflow.com/a/24757284/1187415
extension String {
init?<C : UnicodeCodec>(codeUnits:[C.CodeUnit], codec : C) {
var codec = codec
var str = ""
var generator = codeUnits.makeIterator()
var done = false
while !done {
let r = codec.decode(&generator)
switch (r) {
case .emptyInput:
done = true
case .scalarValue(let val):
str.unicodeScalars.append(val)
case .error:
return nil
}
}
self = str
}
}
can be used with UTF-8, UTF-16 and UTF-32 input. In your case it would be
let myUInt32Array: [UInt32] = [72, 101, 108, 108, 111, 128049, 127465, 127466]
let myString = String(codeUnits: myUInt32Array, codec : UTF32())!
print(myString) // Hello🐱🇩🇪
NSUTF32LittleEndianStringEncoding in your answer? Do I need to change anything when saving strings to a file or sending them over the network? If I just use the Swift classes can I avoid worrying about big/little endian encoding?