本文共 4541 字，大约阅读时间需要 15 分钟。
对比一下两种语言的语法，以防止自己搞混。以便于自己记忆。
肯定是不全的，随时增删改查。
在线文档;
| 概念 | swift5 | C++ |
| 打印 | print( "Hello World") | printf("Hello World"); |
| 关键字, 数据类型 | var let enum : Optional struct : Bool、Int、Float、Double、Character, String、Array、Dictionary、Set class :
Void
Int8、Int16、Int32、Int64、UInt8、UInt16、UInt32、UInt64 |
asm auto bool break case catch char class const const_cast Continue default delete do double dynamic_cast else enum explicit export extern false float for friend goto if inline int long mutable namespace new operator private protected public register reinterpret_cast return short signed sizeof static static_cast struct switch template this throw true try typedef typeid typename union unsigned using virtual void volatile wchar_t while |
| 变量 | var value = 10 //整形 自动识别类型 print(value)
var value = "hello world" //字符串 print(value)
var value = [1,3,5,7,9] //数组 print(value)
var dic = ["length":1, "width":2, "height":3] //字典 print(dic)
var stu = ("0001","man",90,"高一9班",170,120) print(stu) //元组 | int value = 10; float value = 10.0
//字符串 const char *st = "The expense of spirit\n";
int ia[10]; //数组
int ia[] = { 0, 1, 2 }; //数组 |
| 常量 | let value = 10 print(value)
let value: Float = 10.5 //指定类型 print(value) | // 缓冲区大小 const int bufSize = 512 |
| if-else | let age = 30 if age > 100 { print("died") }else if age > 60 { print("old") }else if age >= 30 { print("married") }else{ print("happy") } | int age = 30; if (age > 100) { printf("died"); }else if( age > 60) { printf("old"); }else if( age >= 30 ){ printf("married"); }else{ printf("happy"); } |
| while | var num = 3 while num > 0 { num = num - 1 print("hello") }
//repeat-while var num = 3 repeat{ num = num - 1 print("hello") } while num > 0 | int num = 3; while (num > 0) { num = num - 1; printf("hello"); }
/do-while int num = 3; do{ num = num - 1; printf("hello"); } while( num > 0 ); |
| for | //i 默认是let , 也可以声明为var for i in 1...5{ print(i) }
for i in 1...5 where i != 3 { print(i) }
let names = ["hello","world","look"] for name in names[0...2] { print(name) } | for(int i = 1; i <=5; ++i){ printf("%d",i); } |
| switch | ||
| 函数 | func getPi() -> Double { return 3.14 }func sum(v1 : Int, v2: Int) -> Int{ return v1+v2 }print(getPi()) print(sum(v1 : 3, v2: 5)) | double getPi() { return 3.14; }int sum( int v1, int v2) { return v1+v2; }printf("%.6f",getPi()); printf("%d",sum(3, 5)); |
| 输入输出参数 | func swapValues(_ v1: inout Int, _ v2: inout Int) { (v1,v2) = (v2,v1) }var v1 = 3 var v2 = 4 swapValues(&v1,&v2) print("v1: \(v1) v2: \(v2)") | 通过 指针 或者 引用 |
| 枚举 | enum Direction : Int{ case north case south case east case west } print(Direction.north) print(Direction.north.rawValue) | enum Direction{ north, south, east, west };
printf("%d",north); printf("%d",south); |
| 获取占用的字节大小 | // 8, 分配占用的空间大小 print(MemoryLayout<Int>.stride)
// 8, 实际用到的空间大小 print(MemoryLayout<Int>.size)
// 8, 对齐参数 print(MemoryLayout<Int>.alignment)
var ret = "helloworld" print(MemoryLayout.stride(ofValue: ret)) | //4 printf("%d",sizeof(int));
|
| 可选项 | ||
| struct | struct Date{ var year:Int var month:Int var day:Int }var date = Date(year:2019, month:11, day:21) print(date)
// struct Date{ var year:Int var month:Int var day:Int init(year: Int, month: Int, day: Int){ self.year = year self.month = month self.day = day } }var date = Date(year:2017, month:11, day:21) print(date)
| |
| class | class Size{ var width = 10 var height = 20 func showSize(){ print("width = \(width),height=\(height)") } }var size = Size() size.showSize() | |
| 闭包表达式 | ||
| 存储属性 和 计算属性 | struct Rect{ var width: Int //存储属性 var area: Int { //计算属性 set{ width = newValue/2 } get{ width*width } }} var rect = Rect(width:5) print(rect.width) //5 print(rect.area) //25rect.area = 20 print(rect.width) //10 | |
| 类型属性 | struct Car{ static var count: Int = 0init(){ Car.count = Car.count + 1 } }var car1 = Car() var car2 = Car() var car3 = Car()print(Car.count) | |
| 继承 | //值类型（枚举、结构体）不支持继承，只有类支持继承 class Animal { var age = 1 } class Dog : Animal { var weight = 2 } class ErHa : Dog { var iq = 3 }var erha = ErHa() print(erha.age) print(erha.weight) print(erha.iq) | |
| 重写实例方法 | class Animal{ func call(){ print("---animal call---") } }class Cat : Animal{ override func call(){ super.call() print("---Cat call---") } }var animal = Animal() animal.call()animal = Cat() animal.call() | |
| 协议（Protocol） | ||
| Any is | protocol Runnable { func run() } class Person{} class Student : Person, Runnable { func run(){ print("student run") } func study(){ print("student study") } }var stu : Any = 10 print(stu is Int) //true stu = "jack" print(stu is String) //true stu = Student() print(stu is Person) //true print(stu is Student) //true print(stu is Runnable) //true | |
| 局部作用域 | do{ //.... } | |
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