带有枚举案例数组的switch语句

Question

我有一个enum案例数组，我想对这些案例运行一个switch语句，但是收到这个错误：'[Enum case''North'在类型[Directions]中找不到。

enum Directions {
  case north
  case west
  case east
  case south

  static let all  = [north, west, east, south]
}

class MyViewController {
    var directions = Directions.all

    func foo () {
        switch directions {
        case .north: // Error here ('Enum case 'North' not found in type '[Directions]')
            print("Going north")
        }
    }
}

Answer 1

首先需要遍历阵列，然后才能使用开关

func foo () {
    for direction in directions {
        switch direction {
        case .north: print("Going north")
        case .west: print("Going west")
        case .east: print("Going east")
        case .south: print("Going south")
        }
    }
}

  

枚举的名称应为单数，因此Direction代替Directions

Answer 2

the problem is that you are comparing a array of Directions type to an Directions enum case. You need to compare a particular element of array as listed below:

enum Directions {

    case north
    case south
    case east
    case west
    static let all  = [north, west, east, south]
}


class MyViewController {
    var dir = Directions.all

    func testing(){

        switch dir[0] {
            case .north:
                 print("north")
            default:
                 print("default")
        }
    }
}

var a = MyViewController()

a.testing()

// out put : north

Answer 3

您可以使用以下方式提及代码

enum Directions {
  case north
  case west
  case east
  case south
}

class MyViewController {

    func foo () {
        switch Directions 
      {
        case Directions.north: 
            print("Going north")
        }
    }
}