写swift一时爽，一直写一直爽~~~

模式匹配

switt中强大的switch case 结合枚举和元祖会有意想不到的作用
枚举：

// 定义个枚举
enum School {
  case Student(name: String, age: Int, address: String?)
  case Teacher(name: String, age: Int, address: String?)
}
// 取一个枚举值
let karl =  School.Student(name: "karl", age: 27, address: "AH")

// 匹配一下
switch student {
case .Student(let name, let age, let address):
  print("\(name) -- \(age) -- \(address)")
default:
  break
}

通配符

这个有意思，和可选链有点混

let student = School.Student(name: "karl", age: 27, address: nil)
let teacher = School.Teacher(name: "wang", age: 50, address: "AH")

// _ :这个值完全不重要，可有可无，是什么我都不关心。
switch student {
case let .Teacher(name, _, _):
    print("name: \(name)")
default: break
} 

// _? :这个值我虽然不用，但是它不能为空
switch student {
case let .Student(name, age, _?):
   print("name: \(name)")
default: break
} 

元祖

吆西，看完上面的概念，来看看元祖‘

// 不管age， 取出name
let people = (age: 27, name: "karl")
switch people {
case (_, let name):
  print(name)
default:
  break
}
// where 语句
switch student {
case let .Student(_, age, _) where age > 30:
  print("\(age)")
default:
  break
}

other

// 来个range看看，爽不爽
let number = 10
switch number {
case 0 ... 7:
  print("0 ... 7")
case 10 ..< 20:
  print("10 ..< 20")
default:
  break
}

参考文章