Swift3.0学习--switch分支及For循环

Switch

OC的switch
- 分支中变量只能是整数值
- 每段语句必须有break

int num;
    switch (num) {
        case 0:
            NSLog(@"输出0");
            break;
        case 1:
            NSLog(@"输出1");
            break;
        case 2:
            NSLog(@"输出2");
            break;
        default:
            break;
    }

Swift的switch
- 变量无要求,可以使任意
- 每段语句不需要break,只有这段语句没有代码的时候才写break
- 多个变量可以用’,’来连接

func switchDemo(num: String){
    switch num {
    case "0":
        print("输出0")
    case "1","2.3":
        break
    default:
        print("不输出")
    }
}

For

OC的for循环

1
2
3

for (NSInteger i = 0; i < <#num#>; i++) {
       <#statements#>
   }

Swift的for循环
- 3.0取消了i++,++i,取而代之的是i+=1
- num = i++ ==> temp=i,num=temp,i=temp+1
- num = ++i ==> i=i+1,num=i

func forDemo() {
    //[0,5)  //前闭后开区间
    for i in 0..<5 {
        print(i)
    }
    //[0,5]  //前开后开区间
    for i in 0...5 {
        print(i)
    }
    //反序遍历
    for i in (0..<10).reversed() {
        print(i)
    }
    //是一种固定的格式,2.0一样,3.0不一样
    let r1 = 0..<5 //CountableRange<Int>
    let r2 = 0...5 //CountableClosedRange<Int>
    
}

2017-06-06