A view of a string’s contents as a collection of Unicode scalar values.
Swift Standard Library
You can access a string’s view of Unicode scalar values by using its unicodeScalars property. Unicode scalar values are the 21-bit codes that are the basic unit of Unicode. Each scalar value is represented by a Unicode.Scalar instance and is equivalent to a UTF-32 code unit.
Some characters that are visible in a string are made up of more than one Unicode scalar value. In that case, a string’s unicodeScalars view contains more elements than the string itself.
You can convert a String.UnicodeScalarView instance back into a string using the String type’s init(_:) initializer.