protocolmagic.swift

class Node {
  let name: String
  init(_ name: String) {
    self.name = name
  }
}

extension RangeReplaceableCollectionType where Generator.Element == Node {
  mutating func node(name: String) -> Node {
    if let firstMatch = self.lazy.filter({ n in n.name == name }).first {
      return firstMatch
    }
    let newNode = Node(name)
    self.append(newNode)
    return newNode
  }
}