DownloadAndDelegate.swift

import Foundation

protocol DownloadDelegate: class {
  func downloadProgressUpdated(for progress: Float)
}
final class Download {
  
  weak var delegate: DownloadDelegate?
  var url: URL
  var downloadTask: URLSessionDownloadTask?
  
  var progress: Float = 0.0 {
    didSet {
      updateProgress()
      if progress == 1 {
        downloadTask = nil
      }
    }
  }
  private func updateProgress() {
    if downloadTask != nil {
      delegate?.downloadProgressUpdated(for: progress)
    }
  }
  
  init(url: URL) {
    self.url = url
  }
}