Swift

简介

• Swift用于开发iOS、OS X、watchOS。结合了C和Objective-C的优点并且不受

数据类型

• int
  • 十进制整型 123
  • 十六进制整型 0x1231f1
• float
  • 2434.34
  • 12.4e6
• double
  • 143.4f
• char
  • 'a'
• 常量

let name = jinchen
let number : Double = 50 指定类型
let apples = 3 
let appleSummary = "I have \(apples) apples"

• 变量

var name = "jinchen"

• 数组

var arr = ["a", "b", "c"]
var arr = []

• 字典

var dict = ["name1" : "value1", "name2" : "value2" ]
var dict = [:]

• 字符串

  • 字面量

  let some = "some things";

  • 空字符串

  var emptyString = ""
  var emptyString = String()
  if emptyString.isEmpty {
      print("Nothing to see here");
  }

  • 字符串可变性

  字面量是常量还是变量确定字符串的可变性
  字符串值类型
  for character in "Dog" {
      print(character);
  }

  • 字符串数量

  let name = "jinchen"
  print("name has (name.count) character")

  • 连接字符串和字符

  let character1 ：Character = "!"
  var welcome = "good morning"
  welcome += character1

  • 字符串插值

  let num = 3
  let message = "(num) times"

  • 比较字符串
    • 字符串相等

    let name1 = "jinchen"
    let name2 = "jinchen"
    if name1 == name2 {
        print("These two strings are considered equal")
    }

    • 字符串前缀、后缀比较 hasPrefix、hasSuffix

    let romeoAndJuliet = {
        "Act 1 AAAAA",
        "Act 1 BBBBB",
        "Act 1 CCCCC",
        "Act 2 AAAAA",
    }
    var act1count = 0
    for scene in romeoAndJuliet {
        if scene.hasPrefix("Act 1") {
            ++act1count
        }
    }
    print(act1count);

  • 字符串大写、小写

  let name = “JinChen”
  let name1 = name.uppercaseString
  let name2 = name.lowercaseString

流程控制

• for循环

  • for- in

  for index in 1...5 { // ...表示序列
      print(index)
  }
  for _ in 1...5 {
      print("HelloWorld")
  }
  let interestingNumbers = [
      "Frime": [2, 3, 5, 7, 11, 13],
      "Equarl": [1, 4, 9, 16, 25]
  ]
  var largest = 0
  for (kind, numbers) in interestingNumbers {
      for number in numbers {
          if(number > largest) {
              largest = number
          }
      }
  }
  print(largest)

  • 增量循环 Swift3 已经删除C样式语句

  for var index1 = 0; index1 < 3; ++index1 {
      print(index1)
  }

• while循环

  • while

  var n = 2
  while n < 100 {
      n = n + 30
  }
  print(n)

  • repeat-while

  var m = 2
  repeat {
      m = m + 30
  } while m < 100
  print(m)

• if语句

var num2 = "jin"
if(num2 == "jinchen") {
    print(1)
} else if(num2 == "jin") {
    print(2)
} else {
    print(3)
}

• switch

let someCharacter : Character = "e"
switch someCharacter {
    case "a", "b":
        print("AA")
    case "e":
        print("BB")
    default:
        print("CC")
}

函数

• 单返回值

func sayHello(personName: String) -> String {
    let message = "Hello (personName)"
    return message
}
print(sayHello(personName: "Jc"))

• 多返回值

func count(string: String) -> (vowels: String, others: String) {
    var vowels = "A", others = "B"
    vowels += string
    others += string
    return (vowels, others)
}
print(count(string: "Jc"))