Real-Time On-Device Replace CoreML Model With Update

ViewController.swift

	@IBAction private func modelVersionPicked() {
		var modelName:String = "";
		switch modelPicker.selectedSegmentIndex {
			case 0:
				modelName = "DeviceWornClsfr_20.mlmodel";
			case 1:
				modelName = "DeviceWornClsfr_20.mlmodel";
			default:
				modelName = "this is going to blow up";
		}
		_ = getModel(modelName: modelName)
	}

	private func getModel(modelName: String) {

		let coremlDir = try! FileManager.default.url(for: .applicationSupportDirectory, in: .userDomainMask, appropriateFor: nil, create: false).appendingPathComponent("3M/CoreML/",isDirectory: true)
		print("CoreML directory at: ",coremlDir.path)

		// setup the URL objects for source and destination
		let urlDest:URL = coremlDir.appendingPathComponent(modelName)
		print("urlDest: ",urlDest.path)

		let urlSource = URL(string: "http://localhost/coreml/" + modelName)
		print("Downloading urlSource from: ",urlSource?.absoluteString as Any)
		print("")

		if (FileManager.default.fileExists(atPath: urlDest.path)) {
			print("")
			print("Deleting ",urlDest.path)
			try! FileManager.default.removeItem(atPath: urlDest.path)
		}

		// setup the alert
		let alert = UIAlertController(title: "Download complete", message: "We have downloaded the file " + modelName + ".", preferredStyle: .alert)

		alert.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))

		print("Downloading ",urlSource?.absoluteURL as Any," to ",urlDest.path)
		downloadModel(url: urlSource!, to: coremlDir, completion: {
			() -> Void in
				self.present(alert, animated: true)
				let modelCompiled:URL = try! MLModel.compileModel(at: urlDest)

				// setup the alert
				let alert = UIAlertController(title: "Model Compiled", message: "We have compiled the model " + modelCompiled.path + ".", preferredStyle: .alert)

				alert.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
				self.present(alert, animated: true)
		})
	}

	func downloadModel(url: URL, to localUrl: URL, completion: @escaping () -> ()) {
		let sessionConfig = URLSessionConfiguration.default
		let session = URLSession(configuration: sessionConfig)
		let request = URLRequest(url: url)


		let task = session.downloadTask(with: request) { (tempLocalUrl, response, error) in
			if let tempLocalUrl = tempLocalUrl, error == nil {
				// Success
				if let statusCode = (response as? HTTPURLResponse)?.statusCode {
					print("Success: \(statusCode)")
				}

				do {
					try FileManager.default.copyItem(at: tempLocalUrl, to: localUrl)
					completion()
				} catch (let writeError) {
					print("error writing file \(localUrl) : \(writeError)")
				}

			} else {
				print("Failure: %@", error?.localizedDescription as Any);
			}
		}
		task.resume()
	}