Swift學習（5）- 字串與字元（程式碼完善版）

let someString = "Some string literal value"  // 字串字面量初始化 String 型別常數

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 til you come to the end; then stop."
        """
print(quotation)
---
output: 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 til you come to the end; then stop."

let singleLineString = "These are the same."
let multiLineString = """
These are the same.
"""
print("單行字串：\(singleLineString)")
print("多行字串：\(multiLineString)")
---
output: 單行字串：These are the same.
多行字串：These are the same.

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."
"""
print("使用了換行符的 quotation：\(softWrappedQuotation)")
---
output: 使用了換行符的 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."

let lineBreaks = """

This string starts with a line break.
It also ends with a line break.

"""
print(lineBreaks)
---
output: 
This string starts with a line break.
It also ends with a line break.

let linesWithIndentation = """
        This line doesn't begin with whitespace.
                This line begins with four spaces.
        This line doesn't begin with whitespace.
        """  // 關閉引號前的空白有 4 個空格
print(linesWithIndentation)
---
output: This line doesn't begin with whitespace.
        This line begins with four spaces.
This line doesn't begin with whitespace.

let wiseWords = "\"Imagination is more important than knowledge.\" - Einstein"
let dollarSign = "\u{24}"  // $，Unicode 標量 U+0024
let blackHeart = "\u{2665}"  // ♥，Unicode 標量 U+2665
let sparklingHeart = "\u{1F496}"  // 💖，Unicode 標量 U+1F496
print(wiseWords)
print(dollarSign, terminator: " ")
print(blackHeart, terminator: " ")
print(sparklingHeart)
---
output: "Imagination is more important than knowledge." - Einstein
$ ♥ 💖

let threeDoubleQuotes = """
        Escaping the first quote \"""
        Escaping all three quotes \"\"\"
        """
print(threeDoubleQuotes)
---
output: Escaping the first quote """
Escaping all three quotes """

let threeMoreDoubleQuotationMarks = #"""
Here are three more double quotes: """
Good! Good!
"""#
print(threeMoreDoubleQuotationMarks)
---
output: Here are three more double quotes: """
Good! Good!

var emptyString = ""  // 空字串字面量
var anotherEmptyString = String()  // 初始化方法
// 兩個字串皆為空且等價

if emptyString.isEmpty {
        print("Nothing to see here.")  // 輸出「Nothing to see here.」
}
---
output: Nothing to see here.

var variableString = "Horse"
variableString += " and carriage"  // variableString 現在為「Horse and carriage」
print(variableString)

let constantString = "Highlander"
//constantString += " and another Hignlander"  // 若取消這行註解，編譯器會報錯：Left side of mutating operator isn't mutable: 'constantString' is a 'let' constant
print(constantString)
---
output: Horse and carriage
Highlander

for character in "Dog!🐶" {
        print(character)
}
// 另外，也可以明確標註為 `Character` 型別並用字元字面量指派，建立獨立的字元常數或變數。
let exclamationMark: Character = "!"
// 字串也可以傳入一個值型別為 `Character` 的陣列來初始化。
let catCharacters: [Character] = ["c", "a", "t", "!", "🐱"]
let catString = String(catCharacters)
print(catString)  // 輸出 "cat!🐱"
---
output: D
o
g
!
🐶
cat!🐱

let string1 = "hello"
let string2 = " jensen"
var welcome = string1 + string2  // welcome 現在等於「hello jensen」
print(welcome)
---
output: hello jensen

var instruction = "look over"
instruction += string2  // instruction 現在等於「look over jensen」
print(instruction)
---
output: look over jensen

let questionMark: Character = "?"
welcome.append(questionMark)  // welcome 現在等於「hello jensen?」
print(welcome)
---
output: hello jensen?

let badStart = """
        one
        two
        """
let end = """
        three
        """
print(badStart + end)  // 輸出兩行：one\ntwothree

let goodStart = """
        one
        two
        
        """
print(goodStart + end)  // 輸出三行：one\ntwo\nthree
---
output: one
twothree
one
two
three

let multiplier = 3
let message = "\(multiplier) times 2.5 is \(Double(multiplier) * 2.5)"  // message 是「3 times 2.5 is 7.5」
print(message)
---
output: 3 times 2.5 is 7.5

print(#"Write an interpolated string in Swift using \(multiplier)."#)  // 輸出「Write an interpolated string in Swift using \(multiplier).」
---
output: Write an interpolated string in Swift using \(multiplier).

print(#"6 times 7 is \#(6 * 7)"#)  // 輸出「6 times 7 is 42」
---
output: 6 times 7 is 42

let eAcute: Character = "\u{E9}"  // é 代表一個單一 Swift Character 值，也代表一個可擴充字形群集，該群集只含一個標量
let combinedEAcute = "\u{65}\u{301}"  // é 代表一個可擴充字形群集，該群集含兩個標量
print("eAcute is \(eAcute) and combinedEAcute is \(combinedEAcute)")
---
output: eAcute is é and combinedEAcute is é

let precomposed: Character = "\u{D55C}"  // 한
let decomposed: Character = "\u{1112}\u{1161}\u{11AB}"  // ᄒ, ᅡ, ᆫ
print("precomposed 的值是 \(precomposed)，decomposed 的值是 \(decomposed)")
---
output: precomposed的值是한，decomposed的值是한

let enclosedEAcute: Character = "\u{E9}\u{20DD}"  // enclosedEAcute 是 é⃝
print(enclosedEAcute)
---
output: é⃝

let regionalIndicatorForHK: Character = "\u{1F1ED}\u{1F1F0}"  // HK
print(regionalIndicatorForHK)  // regionalIndicatorForHK 是 🇭🇰
---
output: 🇭🇰

let unusualMenagerie = "Koala 🐨, Snail 🐌, Penguin 🐧, Dromedary 🐫"
print("unusualMenagerie has \(unusualMenagerie.count) characters.")  // 輸出「unusualMenagerie has 40 characters.」
---
output: unusualMenagerie has 40 characters.

var word = "cafe"
print("The number of characters in \(word) is \(word.count).")  // 輸出「The number of characters in cafe is 4.」

word += "\u{301}"
print("The number of characters in \(word) is \(word.count).")  // 輸出「The number of characters in café is 4.」
---
output: The number of characters in cafe is 4.
The number of characters in café is 4.

let greeting = "Jensen Jon!"
print("greeting's first character is \(greeting[greeting.startIndex]).")  // J
print("The character before greeting's endIndex is \(greeting[greeting.index(before: greeting.endIndex)])")  // !
print("The character after greeting's startIndex is \(greeting[greeting.index(after: greeting.startIndex)])")  // e
print("The character with a offset of 7 from greeting's startIndex is \(greeting[greeting.index(greeting.startIndex, offsetBy: 7)])")  // J
---
output: greeting's first character is J.
The character before greeting's endIndex is !
The character after greeting's startIndex is e
The character with a offset of 7 from greeting's startIndex is J

//greeting[greeting.endIndex]  // 若取消註解，執行時會報錯：Fatal error: String index is out of bounds
//greeting.index(after: greeting.endIndex)  // 若取消註解，執行時會報錯：Fatal error: String index is out of bounds

for index in greeting.indices {
        print("\(greeting[index])", terminator: " ")  // 輸出「J e n s e n   J o n !」
}
print("")
---
output: J e n s e n   J o n ! 

var friendlyGreeting = "hello"
friendlyGreeting.insert("!", at: friendlyGreeting.endIndex)  // friendlyGreeting 現在等於「hello!」

friendlyGreeting.insert(contentsOf: " there", at: friendlyGreeting.index(before: friendlyGreeting.endIndex))  // friendlyGreeting 現在等於「hello there!」

friendlyGreeting.remove(at: friendlyGreeting.index(before: friendlyGreeting.endIndex))  // friendlyGreeting 現在等於「hello there」

let range = friendlyGreeting.index(friendlyGreeting.endIndex, offsetBy: -6)..<friendlyGreeting.endIndex
friendlyGreeting.removeSubrange(range)  // friendlyGreeting 現在等於「hello」
print(friendlyGreeting)
---
output: hello

let niceGreeting = "Hello, Jensen!"
let index = niceGreeting.firstIndex(of: ",") ?? niceGreeting.endIndex
let beginning = greeting[..<index]  // beginning 的值是「Hello」
// 把結果轉成 String 以便長期儲存。
let newString = String(beginning)
print("newString is \(newString).")
---
output: newString is Jense.

let aQuotation = "We're a lot alike, you and I."
let sameQuotation = "We're a lot alike, you and I."
if aQuotation == sameQuotation {
        print("These two strings are considered equal.")  // 輸出「These two strings are considered equal.」
}
---
output: These two strings are considered equal.

let eAcuteQuestion = "Voluez-vous un caf\u{E9}?"
let combinedEAcuteQuestion = "Voluez-vous un caf\u{65}\u{301}?"

if eAcuteQuestion == combinedEAcuteQuestion {
        print("These two strings are considered equal.")  // 輸出「These two strings are considered equal.」
}
---
output: These two strings are considered equal.

let latinCapitialLetterA: Character = "\u{41}"
let cyrillicCapitalLetterA: Character = "\u{410}"

if latinCapitialLetterA != cyrillicCapitalLetterA {
        print("These two characters are not equivalent.")  // 輸出「These two characters are not equivalent.」
}
---
output: These two characters are not equivalent.

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"
]

var act1SceneCount = 0
for scene in romeoAndJuliet {
        if scene.hasPrefix("Act 1 ") {
                act1SceneCount += 1
        }
}
print("There are \(act1SceneCount) scenes in Act 1.")
---
output: There are 5 scenes in Act 1.

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")
---
output: 6 mansion scenes; 2 cell scenes

let dogString = "Dog‼🐶"

for codeUnit in dogString.utf8 {
        print("\(codeUnit) ", terminator: "")
}
print("")
---
output: 68 111 103 226 128 188 240 159 144 182 

for codeUnit in dogString.utf16 {
        print("\(codeUnit) ", terminator: "")
}
print("")
---
output: 68 111 103 8252 55357 56374

for scalar in dogString.unicodeScalars {
        print("\(scalar.value) ", terminator: "")
}
print("")
---
output: 68 111 103 8252 128054 

for scalar in dogString.unicodeScalars {
        print("\(scalar) ")
}
---
output: D 
o 
g 
‼ 
🐶