[swift学习之二]基本语法练习

野性酷女 2022-08-21 13:54 199阅读 0赞

//: Playground - noun: a place where people can play
    
    import UIKit
    
    /*注意点
     1:  Swift语言使用var定义变量，但和别的语言不同，Swift里不会自动给变量赋初始值，也就是说变量不会有默认值，所以要求使用变量之前必须要对其初始化。如果在使用变量之前不进行初始化就会报错：
     2:  String是值类型，NSString是引用类型
     3:  Bool值的比较不能用nil，false!=nil
     4:  字典和数组支持了基本的数据类型,NSNumber没啥用了～
     5:  三目的运算符要和变量间加空格，否则会吧？认为解包（自己的理解啊～）
     */
    //------------------------//
    /*亮点1:变量或常量的类型可以省略，会根据注意点1，判断类型*/
    let label:String = "my old is"
    let myOld = 33
    print(label + String(myOld))
    for character in label.characters {
        print("\(character)\n")
    }
    //------------------------//
    var optionalString: String? = "Hello"
    var OptionalName = optionalString?.uppercaseString
    if let name = OptionalName {
        /*如果不判断，就得加！解包*/
        print(name + optionalString!)
        if let name2 = optionalString{
            print(name2 + " Hello \(name)" )
        }
    }
    //------------------------//
    var nickName: String? = "ss"
    var fullName: String? = "John Appleseed"
    /*??如果可选的值丢失，用默认的值替代，只针对带？的变量或常量*/
    let informalGreeting = "Hi \(fullName! ?? nickName!)"
    if let a = fullName where (fullName?.hasPrefix("John A") == true),let b = nickName {
        print(a+b)
    }
    //------------------------//
    /*亮点2:和oc的block遍历有一拼～*/
    let simpleArr: Array<Int> = [20,10,30,40]
    for (index: Int,value) in simpleArr.enumerate()
    {
        print("\(index):\(value)")
    }
    //------------------------//
    /*simpleArrB复制了一份，并且不可变*/
    var simpleArrA:NSMutableArray = NSMutableArray(array: [20])
    let simpleArrB:NSArray? = simpleArrA.copy() as? NSArray
    simpleArrA.insertObject(30, atIndex: 0)
    /*亮点3:if条件let＋where*/
    if (simpleArrB != nil) && (simpleArrB?.count == 1){
        for a in simpleArrB!{
            print(a)
        }
    }
    if let bufB = simpleArrB where simpleArrB?.count == 1{
        for a in bufB{
            print(a)
        }
    }
    //------------------------//
    var Mutabledic:Dictionary = [Int:Array<Int>]()
    Mutabledic[3] = [10,20]
    Mutabledic[4] = [30,40]
    mainFor:for(key,values) in Mutabledic{
        for key in values{
            if key > 0{
                print(key)
    /*亮点4:Break还可以这么干～*/
                break mainFor
            }
        }
    }
    for a in Mutabledic
    {
    /*亮点5,Pair的值直接索引了～*/
        print(a.1)
        print(a.0)
        break
    }
    //------------------------//
    let vegetable = "red pepper"
    /*亮点6:switch居然支持字符串，而且还有个let a where 赋值*/
    switch vegetable {
    case let x where x.hasPrefix("red"):
        print("Is it a spicy \(vegetable)?")
    case "celery":
        print("Add some raisins and make ants on a log.")
    case "cucumber", "watercress":
        print("That would make a good tea sandwich.")
    /*没有default也报错～*/
    default:
        print("Everything tastes good in soup.")
    }
    //------------------------//
    var total: Int = 0
    /*亮点7:For的开闭区间还能这样表示*/
    for i in 0..<4{/*0+1+2+3*/
        total+=i
    }
    print(total)
    total = 0
    for i in 0...4{/*0+1+2+3+4*/
        total+=i
    }
    print(total)
    //------------------------//
    /*函数参数用逗号隔开，oc是空格。返回值类型写在了后面，而且还用了c++的箭头～*/
    func greet(name:String,day:String)->String
    {
        return "name:\(name),day:\(day)"
    }
    print(greet("Hello", day: "World"))
    //------------------------//
    /*亮点8:函数的返回值还可以这么写，这是要上天啊～*/
    func CalculateStatistics(values:[Int])->(max:Int,min:Int,sum:Int)
    {
        var vMax:Int=values[0]
        var vMin:Int=values[0]
        var vSum:Int = 0
        for element in values {
            if element>vMax {
                vMax = element
            }
            if element<vMin {
                vMin=element
            }
            vSum+=element
        }
        return(vMax,vMin,vSum)
    }
    let rValue = CalculateStatistics([10,20,50])
    print("sum:\(rValue.sum)max:\(rValue.max)min:\(rValue.1)")
    //------------------------//
    /*亮点9:参数可以这样写，c＋＋早支持。0个和多个都行，其实就是[Int]。但实参可以分开～*/
    func CalculateSum(value1:Int...)->Int
    {
        var sum = 0
        for a in value1 {
            sum+=a
        }
        return sum
    }
    print(CalculateSum(3,4,6))
    //------------------------//
    /*亮点10:函数嵌套的语法简单明了啊。比oc的block强。下面我写的block，写法不一定最优啊～
     NSInteger (^CaluelateSum)(NSInteger) = ^NSInteger(NSInteger value){
        NSInteger vValue = 0;
        NSInteger (^Square) (NSInteger) = ^NSInteger (NSInteger v){
          return v*v;
        };
        vValue = Square(value);
        return vValue + 2;
     };
     NSLog(@"%ld",CaluelateSum(8));
     */
    func funcNested(value1:Int)->Int
    {
        var vValue=0;
        func Square(v:Int)->Int
        {
            return v*v;
        }
        vValue = Square(value1)
        return vValue + 2;
    }
    print(funcNested(5))
    //------------------------//
    /*亮点11:函数当返回值。写法相当简单明了，比block强点儿。下面我写的block，写法不一定最优啊～
     typedef NSInteger(^funReturn)(NSInteger);
     funReturn(^CaluelateSum)(NSInteger) = ^funReturn(NSInteger value){
         NSInteger (^Square) (NSInteger) = ^NSInteger (NSInteger v){
           return v*value;
         };
     return Square;
     };
     funReturn rReturn = CaluelateSum(7);
     NSLog(@"%ld",rReturn(8));结果：56
     */
    func ReturnFun(AName:String)->((aValue:String)->String)
    {
        func RealFun(aValue:String)->String
        {
            return AName + " " + aValue + " ByLYQ"
        }
        return RealFun
    }
    let rFun = ReturnFun("Hello")
    print(rFun(aValue: "World"))
    //------------------------//
    /*亮点12:函数当参数以及函数的匿名写法。现在脑子有点乱，先静静～～*/
    func HasByConditionNumber(Source:[Int],Condition:(Int)->Bool)->Bool
    {
        for a in Source {
            if Condition(a){
                return true
            }
        }
        return false
    }
    let haveMoreThan20 = HasByConditionNumber([1,2,30], Condition: {
        (A:Int)->Bool in
        return A>20
    })
    print(haveMoreThan20 ?"有": "没有")
    //------------------------//
    /*这个放这里不太合适，突然到泛型，泛型约束了。暂时先这样吧，以后再说。
     注意
     1:没有以前的Container协议了，这里还没弄清楚，因为以前什么样，我也不知道～
     2:_ArrayType不能用CollectionType协议替代，原因是count返回值类型
     */
    func allItemsMatch<C1, C2
        where C1:_ArrayType, C2:_ArrayType,
        C1.Generator.Element:Equatable,
        C1.Generator.Element == C2.Generator.Element>
        (someContainer: C1, anotherContainer: C2) -> Bool {
        if someContainer.count != anotherContainer.count {
            return false
        }
        for i in 0..<anotherContainer.count {
            if anotherContainer[i] != someContainer[i]{
                return false
            }
        }
        return true;
    }
    print(allItemsMatch([1,2,3], anotherContainer: [1,2,3,5]) ?"相同" :"不同")

初次学swift，希望以后别接触别等语言了，快乱套了。

如果以后就用swift混饭吃，抱苹果大腿，该多好。

参考：https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift\_Programming\_Language/GuidedTour.html\#//apple\_ref/doc/uid/TP40014097-CH2-ID1