I have an array of unicode scalars (Type is [UnicodeScalar])
like:
let array = [UnicodeScalar("f")!, UnicodeScalar("o")!, UnicodeScalar("o")!]
or
let array2 = "bar".unicodeScalars
how can I convert efficiently these arrays into a strings again?
Expect:
let string1 = ?? // "foo"
let string2 = ?? // "bar"
The second case is simpler because array2 is a UnicodeScalarView
and not an array:
let array2 = "bar".unicodeScalars
let str2 = String(array2)
print(str2) // bar
If you have an array (or any sequence) of Unicode scalars then you can start with an empty string
and append the elements to its unicodeScalars view:
let array = [UnicodeScalar("f")!, UnicodeScalar("o")!, UnicodeScalar("o")!]
// Or: let array: [UnicodeScalar] = ["f", "o", "o"]
var str1 = ""
str1.unicodeScalars.append(contentsOf: array)
print(str1) // foo
Of course you can define a custom extension for that purpose:
extension String {
init<S: Sequence>(unicodeScalars ucs: S)
where S.Iterator.Element == UnicodeScalar
{
var s = ""
s.unicodeScalars.append(contentsOf: ucs)
self = s
}
}
let str1 = String(unicodeScalars: array)
let array: [UnicodeScalar] = ["f", "o", "o"]You can use this extension from @dfri to initialize a string from a UnicodeScalar sequence as follow:
extension Sequence where Element == UnicodeScalar {
var string: String { .init(String.UnicodeScalarView(self)) }
}
let array: [UnicodeScalar] = ["f", "o", "o"]
print(array.string) // "foo\n"
Another way to convert [UnicodeScalar] to String:
let array = [UnicodeScalar("f")!, UnicodeScalar("o")!, UnicodeScalar("o")!]
let string1 = String(array.map{Character($0)})
print(string1 == "foo") //->true
With Swift 5, you can use one of the following ways in order to get a string from a collection of Unicode scalars.
String's init(_:) initializerString 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
String's init(_:) initializerString 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
String.UnicodeScalarView's append(contentsOf:) methodIf 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
Character's init(_:) initializerAnother 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
