Very basic set in Swift

Set.swift

class Set<T: Hashable>: Sequence, Printable {
  var dictionary = Dictionary<T, Bool>()  // private

  func addElement(newElement: T) {
    dictionary[newElement] = true
  }

  func removeElement(element: T) {
    dictionary[element] = nil
  }

  func containsElement(element: T) -> Bool {
    return dictionary[element] != nil
  }

  func allElements() -> T[] {
    return Array(dictionary.keys)
  }

  var count: Int {
    return dictionary.count
  }

  func unionSet(otherSet: Set<T>) -> Set<T> {
    var combined = Set<T>()

    for obj in dictionary.keys {
      combined.dictionary[obj] = true
    }

    for obj in otherSet.dictionary.keys {
      combined.dictionary[obj] = true
    }

    return combined
  }

  func generate() -> IndexingGenerator<Array<T>> {
    return allElements().generate()
  }

  var description: String {
    return dictionary.description
  }
}