Example of an easier string in Swift (not optimized)

EasyString.swift

/*
 Copyright 2017 Google Inc.

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

 https://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
class EasyStringIterator : IteratorProtocol {
  var _index:Int = -1
  var _characters : [Character]

  init(_ characters: [Character]) {
    _characters = characters
  }

  func next() -> Character? {
    if (_index >= _characters.count - 1) {
      return nil
    }
    else {
      _index = _index + 1
      return _characters[_index]
    }
  }
}

class EasyString :CustomStringConvertible, Sequence {
  var _characters : [Character]

  init(_ str:String) {
    _characters = Array(str)
  }

  public var description: String {
    return String(_characters)
  }

  subscript(index:Int) -> Character {
    get {
      return _characters[index]
    }
    set(newElm) {
      _characters[index] = newElm
    }
  }

  func makeIterator() -> EasyStringIterator {
    return EasyStringIterator(_characters)
  }

  static func +(left: EasyString, right: EasyString) -> EasyString {
    return EasyString(left.description + right.description)
  }

  static func +(left: EasyString, right: String) -> EasyString {
    return EasyString(left.description + right)
  }

}