EnumCollection.swift

//
//  EnumCollection.swift
//  Created by Wanbok Choi on 2017. 4. 12..
//

protocol EnumCollection: Hashable {
  static var iterator: AnyIterator<Self> { get }
  static var allValues: [Self] { get }
}

extension EnumCollection {
  static var iterator: AnyIterator<Self> {
    var raw = 0
    return AnyIterator {
      let next = withUnsafeBytes(of: &raw) { $0.load(as: `Self`.self) }
      guard next.hashValue == raw else { return nil }
      raw += 1
      return next
    }
  }
  
  static var allValues: [Self] {
    return Array(self.iterator)
  }
}


/// Example
enum TestEnum: String, EnumCollection {
  case one = "one"
  case two = "two"
  case three = "three"
}

TestEnum.allValues // [one, two, three]

for number in TestEnum.iterator {
  print(number)
} // print one, two, three

TestEnum.iterator.forEach {
  print($0)
} // print one, two, three