Strings and Characters
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String Literals
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let someString = "Some string literal value"
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Multiline String Literals
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let quotation = """
The White Rabbit put on his spectacles. "Where shall I begin,
please your Majesty?" he asked.
"Begin at the beginning," the King said gravely, "and go on
till you come to the end; then stop."
"""
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let singleLineString = "These are the same."
let multilineString = """
These are the same.
"""
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let softWrappedQuotation = """
The White Rabbit put on his spectacles. "Where shall I begin, \
please your Majesty?" he asked.
"Begin at the beginning," the King said gravely, "and go on \
till you come to the end; then stop."
"""
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let lineBreaks = """
This string starts with a line break.
It also ends with a line break.
"""
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Special Characters in String Literals
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let wiseWords = "\"Imagination is more important than knowledge\" - Einstein"
// "Imagination is more important than knowledge" - Einstein
let dollarSign = "\u{24}" // $, Unicode scalar U+0024
let blackHeart = "\u{2665}" // ♥, Unicode scalar U+2665
let sparklingHeart = "\u{1F496}" // π, Unicode scalar U+1F496
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let threeDoubleQuotationMarks = """
Escaping the first quotation mark \"""
Escaping all three quotation marks \"\"\"
"""
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Extended String Delimiters
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let threeMoreDoubleQuotationMarks = #"""
Here are three more double quotes: """
"""#
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Initializing an Empty String
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var emptyString = "" // empty string literal
var anotherEmptyString = String() // initializer syntax
// these two strings are both empty, and are equivalent to each other
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if emptyString.isEmpty {
print("Nothing to see here")
}
// Prints "Nothing to see here"
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String Mutability
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var variableString = "Horse"
variableString += " and carriage"
// variableString is now "Horse and carriage"
let constantString = "Highlander"
constantString += " and another Highlander"
// this reports a compile-time error - a constant string cannot be modified
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Working with Characters
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for character in "Dog!πΆ" {
print(character)
}
// D
// o
// g
// !
// πΆ
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let exclamationMark: Character = "!"
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let catCharacters: [Character] = ["C", "a", "t", "!", "π±"]
let catString = String(catCharacters)
print(catString)
// Prints "Cat!π±"
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Concatenating Strings and Characters
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let string1 = "hello"
let string2 = " there"
var welcome = string1 + string2
// welcome now equals "hello there"
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var instruction = "look over"
instruction += string2
// instruction now equals "look over there"
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let exclamationMark: Character = "!"
welcome.append(exclamationMark)
// welcome now equals "hello there!"
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let badStart = """
one
two
"""
let end = """
three
"""
print(badStart + end)
// Prints two lines:
// one
// twothree
let goodStart = """
one
two
"""
print(goodStart + end)
// Prints three lines:
// one
// two
// three
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String Interpolation
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let multiplier = 3
let message = "\(multiplier) times 2.5 is \(Double(multiplier) * 2.5)"
// message is "3 times 2.5 is 7.5"
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print(#"Write an interpolated string in Swift using \(multiplier)."#)
// Prints "Write an interpolated string in Swift using \(multiplier)."
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print(#"6 times 7 is \#(6 * 7)."#)
// Prints "6 times 7 is 42."
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Extended Grapheme Clusters
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let eAcute: Character = "\u{E9}" // é
let combinedEAcute: Character = "\u{65}\u{301}" // e followed by ́
// eAcute is é, combinedEAcute is é
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let precomposed: Character = "\u{D55C}" // ν
let decomposed: Character = "\u{1112}\u{1161}\u{11AB}" // ᄒ, ᅡ, ᆫ
// precomposed is ν, decomposed is 한
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let enclosedEAcute: Character = "\u{E9}\u{20DD}"
// enclosedEAcute is é⃝
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let regionalIndicatorForUS: Character = "\u{1F1FA}\u{1F1F8}"
// regionalIndicatorForUS is πΊπΈ
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Counting Characters
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let unusualMenagerie = "Koala π¨, Snail π, Penguin π§, Dromedary πͺ"
print("unusualMenagerie has \(unusualMenagerie.count) characters")
// Prints "unusualMenagerie has 40 characters"
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var word = "cafe"
print("the number of characters in \(word) is \(word.count)")
// Prints "the number of characters in cafe is 4"
word += "\u{301}" // COMBINING ACUTE ACCENT, U+0301
print("the number of characters in \(word) is \(word.count)")
// Prints "the number of characters in café is 4"
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String Indices
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let greeting = "Guten Tag!"
greeting[greeting.startIndex]
// G
greeting[greeting.index(before: greeting.endIndex)]
// !
greeting[greeting.index(after: greeting.startIndex)]
// u
let index = greeting.index(greeting.startIndex, offsetBy: 7)
greeting[index]
// a
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greeting[greeting.endIndex] // Error
greeting.index(after: greeting.endIndex) // Error
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for index in greeting.indices {
print("\(greeting[index]) ", terminator: "")
}
// Prints "G u t e n T a g ! "
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Inserting and Removing
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var welcome = "hello"
welcome.insert("!", at: welcome.endIndex)
// welcome now equals "hello!"
welcome.insert(contentsOf: " there", at: welcome.index(before: welcome.endIndex))
// welcome now equals "hello there!"
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welcome.remove(at: welcome.index(before: welcome.endIndex))
// welcome now equals "hello there"
let range = welcome.index(welcome.endIndex, offsetBy: -6)..<welcome.endIndex
welcome.removeSubrange(range)
// welcome now equals "hello"
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Substrings
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let greeting = "Hello, world!"
let index = greeting.firstIndex(of: ",") ?? greeting.endIndex
let beginning = greeting[..<index]
// beginning is "Hello"
// Convert the result to a String for long-term storage.
let newString = String(beginning)
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String and Character Equality
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let quotation = "We're a lot alike, you and I."
let sameQuotation = "We're a lot alike, you and I."
if quotation == sameQuotation {
print("These two strings are considered equal")
}
// Prints "These two strings are considered equal"
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// "Voulez-vous un café?" using LATIN SMALL LETTER E WITH ACUTE
let eAcuteQuestion = "Voulez-vous un caf\u{E9}?"
// "Voulez-vous un café?" using LATIN SMALL LETTER E and COMBINING ACUTE ACCENT
let combinedEAcuteQuestion = "Voulez-vous un caf\u{65}\u{301}?"
if eAcuteQuestion == combinedEAcuteQuestion {
print("These two strings are considered equal")
}
// Prints "These two strings are considered equal"
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let latinCapitalLetterA: Character = "\u{41}"
let cyrillicCapitalLetterA: Character = "\u{0410}"
if latinCapitalLetterA != cyrillicCapitalLetterA {
print("These two characters are not equivalent.")
}
// Prints "These two characters are not equivalent."
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Prefix and Suffix Equality
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let romeoAndJuliet = [
"Act 1 Scene 1: Verona, A public place",
"Act 1 Scene 2: Capulet's mansion",
"Act 1 Scene 3: A room in Capulet's mansion",
"Act 1 Scene 4: A street outside Capulet's mansion",
"Act 1 Scene 5: The Great Hall in Capulet's mansion",
"Act 2 Scene 1: Outside Capulet's mansion",
"Act 2 Scene 2: Capulet's orchard",
"Act 2 Scene 3: Outside Friar Lawrence's cell",
"Act 2 Scene 4: A street in Verona",
"Act 2 Scene 5: Capulet's mansion",
"Act 2 Scene 6: Friar Lawrence's cell"
]
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var act1SceneCount = 0
for scene in romeoAndJuliet {
if scene.hasPrefix("Act 1 ") {
act1SceneCount += 1
}
}
print("There are \(act1SceneCount) scenes in Act 1")
// Prints "There are 5 scenes in Act 1"
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var mansionCount = 0
var cellCount = 0
for scene in romeoAndJuliet {
if scene.hasSuffix("Capulet's mansion") {
mansionCount += 1
} else if scene.hasSuffix("Friar Lawrence's cell") {
cellCount += 1
}
}
print("\(mansionCount) mansion scenes; \(cellCount) cell scenes")
// Prints "6 mansion scenes; 2 cell scenes"
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Unicode Representations of Strings
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let dogString = "Dog‼πΆ"
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UTF-8 Representation
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for codeUnit in dogString.utf8 {
print("\(codeUnit) ", terminator: "")
}
print("")
// Prints "68 111 103 226 128 188 240 159 144 182 "
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UTF-16 Representation
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for codeUnit in dogString.utf16 {
print("\(codeUnit) ", terminator: "")
}
print("")
// Prints "68 111 103 8252 55357 56374 "
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Unicode Scalar Representation
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for scalar in dogString.unicodeScalars {
print("\(scalar.value) ", terminator: "")
}
print("")
// Prints "68 111 103 8252 128054 "
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for scalar in dogString.unicodeScalars {
print("\(scalar) ")
}
// D
// o
// g
// ‼
// πΆ
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