Swift5 vs C/C++ (未完待续)

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;   https://devdocs.io/

 

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.stride)   // 8, 实际用到的空间大小 print(MemoryLayout.size)   // 8, 对齐参数 print(MemoryLayout.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)     //25 rect.area = 20 print(rect.width)    //10
类型属性	struct Car{     static var count: Int = 0     init(){         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{     //.... }