Convert Array of UnicodeScalar into String in Swift

With Swift 5, you can use one of the following ways in order to get a string from a collection of Unicode scalars.

#1. Using String's init(_:) initializer

String has an init(_:) initializer with the following declaration:

init(_ unicodeScalars: String.UnicodeScalarView)

Creates a string corresponding to the given collection of Unicode scalars.

The Playground sample code below shows how to use init(_:) in order to get a String instance from a String.UnicodeScalarView instance:

let string = "foo"
let unicodeScalarView = string.unicodeScalars

let newString = String(unicodeScalarView)
print(newString) // prints: foo

If you initially have an array of Unicode scalars, you can convert it first to a String.UnicodeScalarView instance using String.UnicodeScalarView's init(_:) initializer:

let scalarsArray = [Unicode.Scalar("f"), Unicode.Scalar("o"), Unicode.Scalar("o")]

let unicodeScalarView = String.UnicodeScalarView(scalarsArray)
let newString = String(unicodeScalarView)
print(newString) // prints: foo

#2. Using String's init(_:) initializer

String has an init(_:) initializer with the following declaration:

init(_ scalar: Unicode.Scalar)

The following Playground sample codes show how to iterate over an array of Unicode scalars using String's init(_:) in order to create a new string:

let scalarsArray = [Unicode.Scalar("f"), Unicode.Scalar("o"), Unicode.Scalar("o")]

let string = scalarsArray.reduce("", { partialResult, scalar in
    return partialResult + String(scalar)
})
print(string) // prints: foo

let scalarsArray = [Unicode.Scalar("f"), Unicode.Scalar("o"), Unicode.Scalar("o")]

let newString = scalarsArray.map(String.init).joined()
print(newString) // prints: foo

#3. Using String.UnicodeScalarView's append(contentsOf:) method

If you have an existing string and want to append the elements of a Unicode scalars array into it, you can use append(contentsOf:):

let scalarsArray = [Unicode.Scalar("f"), Unicode.Scalar("o"), Unicode.Scalar("o")]

var newString = ""
newString.unicodeScalars.append(contentsOf: scalarsArray)
print(newString) // prints: foo

#4. Using Character's init(_:) initializer

Another approach would consist of iterating over a collection of Unicode scalars, convert them into characters (using Character's init(_:) initializer) then create a new string from those characters:

let scalarsArray = [Unicode.Scalar("f"), Unicode.Scalar("o"), Unicode.Scalar("o")]

let charactersArray = scalarsArray.map(Character.init)
let newString = String(charactersArray)
print(newString) // prints: foo