ios

约 493 字大约 2 分钟

2020-06-25

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"))