Swift语法入门 1

Swift 基本语法快速入门

单行注释：//
常量和变量
1
2

let constant = 45
var variate = 45 //变量的定义

显示定义和推断定义

1 2	let constant: Int = 45 //显示：告诉是Int类型 let constant: Int = 45 //推断：让解释器推断出是Int类型

Float和Double；Double有更多的精确

1 2	var aaa = 6.7 //默认推断为double var aaa:Float = 6.7 //用float得显示定义

Bools类型；Swift 中使用 true/false作为布尔值

1 2	let onSaleInferred = true let onSaleExplicit: Bool = false

Character和String

var s: Character = "e"//字母
var str: String = "ee" //字符串
print(s) //基本print语句
print("a+b+c+d+(s)+(str)") //字符串插值用

If语句

var is_great = true
if(is_great){
    print("I am a great man~~")
}

类

class  {
    let legNum = 2
    var name = "Mtax"
}
var p = Person()
print(p.name) // Mtax
print(p.legNum) // 2
p.name = "Manggv Tax"
p.legNum = 4 // 会报错
print(p.name) // Manggv Tax
print(p.legNum) // 2

类的继承

class Student:  {
    var stuNo: Int = 12
}
var studentOne = Student()
print(studentOne.name) //Mtax
print(studentOne.stuNo) //12

函数

//定义函数
func test_func() {
    print(< 大专栏  Swift语法入门 1span class="string">"testing the env")
}
test_func() //testing the env
//函数传参
func test_atr(num: Int, name: String) {
    print(num)
}
test_atr(4) //4
//函数返回值指定
func test_return(num: Int) -> String {
    return String(num)
}   
test_return(4) //4
//多参数多返回值
func test_mul_return(n: Int,age: Int = 20) -> (name: String, age: Int) {
    print(n, age)
    return ("er", age)
}
var tt = test_mul_return(4,age:6)

类的初始化

class TestCase {
    let b: Int
    var a: Double
    init(a: Double){
        print("创建对象开始")
        self.a = a
        self.b = 4
        print("创建对象完毕")
    }
}
var t = TestCase(a:5)
print(t.a) //5.0

数组及For遍历

var l = [3,4.5,7] // 等同于下式
var ll: [Double] = [3,4.5,7] // 等同于下式
var llll: Array<Double> = [3,4.5,7] // 等同于上式

//遍历数组元素
for l in llll {
    print("value", l)
}
// 范围操作符
var listA = 1...5 //(a...b) 定义从a到b范围内的值,结果是1,2,3,4,5
var listB = 1..<5 //(a...b) 定义从a到b的值,结果是1,2,3,4

//枚举
for l in 0..<llll.count{
    print("index", l)
    print("value", llll[l])
}

字典

var d = [String: Double]()
d["age": 45]
var dd: [String: Double] = ["age": 34, "num": 67]
print(dd["num"], dd.count)

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