observable pattern pseudo code in swift

observable.swift

class ViewController {
  var observable<[String]>
  
  public var viewModel: ViewModel? {
    didSet {
      self.observable = Observable(viewModel?.someProperty)
      self.observable.bind { [unowned self] (someProperty) in
        if let dataSource = self.dataSource {
          dataSource.someProperty = someProperty
        }
      }
    }
  }
}

class ViewModel {
  var someProperty = [String]()
}