Swift Language Tutorial => Strings and Characters

Syntax

String.characters // Returns an Array of the characters in the String
String.characters.count // Returns the number of characters
String.utf8 // A String.UTF8View, returns the UTF-8 character points in the String
String.utf16 // A String.UTF16View, returns the UTF-16 character points in the String
String.unicodeScalars // A String.UnicodeScalarView, returns the UTF-32 character points in the String
String.isEmpty // Returns true if the String does not contain any text
String.hasPrefix(String) // Returns true if the String is prefixed with the argument
String.hasSuffix(String) // Returns true if the String is suffixed with the argument
String.startIndex // Returns the Index that corresponds to the first character in the string
String.endIndex // Returns the Index that corresponds to the spot after the last character in the string
String.components(separatedBy: String) // Returns an array containing the substrings separated by the given separator string
String.append(Character) // Adds the character (given as argument) to the String

Remarks

A String in Swift is a collection of characters, and by extension a collection of Unicode scalars. Because Swift Strings are based on Unicode, they may be any Unicode scalar value, including languages other than English and emojis.

Because two scalars could combine to form a single character, the number of scalars in a String is not necessarily always the same as the number of characters.

For more information about Strings, see The Swift Programming Language and the String Structure Reference.

For implementation details, see "Swift String Design"