【学习】重学Swift5-运算符&流程控制

三、流程控制

1. for-in

   for i in 0..3 {
     
   }
   
   for c in "hello world" {
     
   }
   
   let names = ["zhangsan", "lisi", "wangwu"]
   for name in names {
     
   }
   
   let numberOfLegs = ["spider" : 8, "ant" : 6, "cat" : 4]
   for (animal, legs) in numberOfLegs {
       print("\(animal) have \(legs) legs")
   }
   
   for t in numberOfLegs {
       print(t.0, t.1)
   }
   
   for _ in 1...5 {
     anser *= 4
   }
   
   // 分段
   let minuteInterval = 5
   for ticket in stride(from: 0, to: 50, by: minuteInterval) {
       print(ticket)
   }
   for ticket in stride(from: 0, through: 50, by: minuteInterval) {
       print(ticket)
   }
   

2. while

   var count = 0
   repeat {
       print(count)
       count += 1
   } while count < 5
   

3. switch

   // swift中 switch语句必须包含全部内容，并且没有隐式贯穿
   // swift case中可以匹配多个值，写成多行，只需用逗号隔开  case "a","A":
   // swift中case还可以进行区间匹配 case 1..<5:
   // swift中case还可以进行元组匹配
   // swift中case还可以进行值绑定 case (let x, 0):
   // swift中case还可以进行where检查  case let(x,y) where x == y:
   

4. 控制转移

   // continue
   // break
   // fallthrough 可以实现oc switvh中的隐式贯穿
   // return
   // throw
   
   // 语句标签
   

5. guard

   guard true else {
       print("when false do something")
   }
   
   print("when true do something")
   

6. 检查API可用性

   if #available(iOS 10, macOS10.12, *) {
       
   } else {
       
   }