Swift编程语言中文教程（三）：字符和字符串

let wiseWords = "\"Imagination is more important than knowledge\" - Einstein"  // "Imagination is more important than knowledge" - Einstein  let dollarSign = "\x24" // $, Unicode scalar U+0024  let blackHeart = "\u2665" // ♥, Unicode scalar U+2665  let sparklingHeart = "\U0001F496" // , Unicode scalar U+1F496

var emptyString = "" // empty string literal  var anotherEmptyString = String() // initializer syntax  // these two strings are both empty, and are equivalent to each other

if emptyString.isEmpty {  println("Nothing to see here")  }  // prints "Nothing to see here"

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

for character in "Dog!" {  println(character)  }  // D  // o  // g  // !  //

let yenSign: Character = "￥"

let unusualMenagerie = "Koala , Snail , Penguin , Dromedary "  println("unusualMenagerie has \(countElements(unusualMenagerie)) characters")  // prints "unusualMenagerie has 40 characters"

let string1 = "hello"  let string2 = " there"  let character1: Character = "!"  let character2: Character = "?"  let stringPlusCharacter = string1 + character1 // equals "hello!"  let stringPlusString = string1 + string2 // equals "hello there"  let characterPlusString = character1 + string1 // equals "!hello"  let characterPlusCharacter = character1 + character2 // equals "!?"

var instruction = "look over"  instruction += string2  // instruction now equals "look over there"  var welcome = "good morning"  welcome += character1  // welcome now equals "good morning!"

let multiplier = 3  let message = "\(multiplier) times 2.5 is \(Double(multiplier) * 2.5)"  // message is "3 times 2.5 is 7.5"

let quotation = "We're a lot alike, you and I."  let sameQuotation = "We're a lot alike, you and I."  if quotation == sameQuotation {  println("These two strings are considered equal")  }  // prints "These two strings are considered equal"  //输出”These two strings are considered equal”

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  }  }  println("There are \(act1SceneCount) scenes in Act 1")  //输出”There are 5 scenes in Act 1”

var mansionCount = 0  var cellCount = 0  for scene in romeoAndJuliet {  if scene.hasSuffix("Capulet's mansion") {  ++mansionCount  } else if scene.hasSuffix("Friar Lawrence's cell") {  ++cellCount  }  }  println("\(mansionCount) mansion scenes; \(cellCount) cell scenes")  // 输出 "6 mansion scenes; 2 cell scenes”

let normal = "Could you help me, please?"  let shouty = normal.uppercaseString  // shouty is equal to "COULD YOU HELP ME, PLEASE?"  let whispered = normal.lowercaseString  // whispered is equal to "could you help me, please?"

for codeUnit in dogString.utf8 {  print("\(codeUnit) ")  }  print("\n")  // 68 111 103 33 240 159 144 182

for codeUnit in dogString.utf16 {  print("\(codeUnit) ")  }  print("\n")  // 68 111 103 33 55357 56374

for scalar in dogString.unicodeScalars {  print("\(scalar.value) ")  }  print("\n")  // 68 111 103 33 128054

for scalar in dogString.unicodeScalars { println("\(scalar) ") }   // D   // o   // g   // !   //