From Objective-C to Xamarin

This talk is about sharing my experience and impressions about the Xamarin platform. It also covers some common mistakes made by obj-c guys who are switching to C#.

Transcript

1. From Objective-C to Xamarin First impressions and common pitfalls Alexander Dodatko 2015
2. Xamarin == C# for Mobile
4. Xamarin's Promise One Codebase — Many Platforms
5. Native UI and UX
7. http://bit.ly/ 1xV1ATx
8. PCL - Portable Class Libraries A standard by M$ and Xamarin
9. Your Code Runs Everywhere If a platform has .NET
10. CI requires NO Simulator
14. Binary Packets
16. • Closures • Optionals • Namespaces • Generics • Type Safety • Functional As Good as Swift
17. You can use exceptions And you should do so
18. Callback Hell http://bit.ly/ 11suEXP
19. http://bit.ly/ 1ryzV4Z
20. Async/Await
21. public class RestApiCallFlow { public static async Task<TResult> LoadRequestFromNetworkFlow <TRequest, THttpResult, Tresult>( TRequest request, IRestApiCallTasks<TRequest, THttpResult, TResult> stages) { string requestUrl = await stages.BuildRequestUrlForRequestAsync(request); // TODO : check cache THttpResult serverResponse = await stages.SendRequestForUrlAsync(requestUrl); TResult parsedData = await stages.ParseResponseDataAsync(serverResponse); return parsedData; } } Async but Looks Linear
22. public class RestApiCallFlow { public static async Task<TResult> LoadRequestFromNetworkFlow <TRequest, THttpResult, Tresult>( TRequest request, IRestApiCallTasks<TRequest, THttpResult, TResult> stages) { string requestUrl = await stages.BuildRequestUrlForRequestAsync(request); try { TResult parsedDataFromCache = await stages.LoadDataFromCacheForRequestAsync(request); return parsedDataFromCache; } catch { // Load from network code } } }
23. public interface IRestApiCallTasks<TRequest, THttpResult, TResult> { Task<string> BuildRequestUrlForRequestAsync(TRequest request); Task<THttpResult> SendRequestForUrlAsync(string requestUrl); Task<TResult> ParseResponseDataAsync(THttpResult httpData); Task<TResult> LoadDataFromCacheForRequestAsync(TRequest request); }
26. Is this lib portable?
27. Same API may Work Differently
29. Xamarin is Slow and has Lots of Memory Leaks From some holy war
30. using (var webclient = new WebClient()) { var imageBytes = webclient.DownloadData(url); return UIImage.LoadFromData(NSData.FromArray(imageBytes)); } http://bit.ly/ 1rMJL3B Image Loading : A Typical Implementation
32. using (var webclient = new WebClient()) { var imageBytes = webclient.DownloadData(url); return UIImage.LoadFromData(NSData.FromArray(imageBytes)); } http://bit.ly/ 1rMJL3B Synchronous
33. using (var webclient = new WebClient()) { var imageBytes = webclient.DownloadData(url); return UIImage.LoadFromData(NSData.FromArray(imageBytes)); } http://bit.ly/ 1rMJL3B Leaks
34. http://bit.ly/1 cay6bO
35. http://bit.ly/1 cay6bO
36. What If I Told You...
37. All Obj-C/Java bindings are IDisposable
38. UIImage, NSData, sockets, threads
39. byte[] data = null; using (Stream response = await session.DownloadResourceAsync(request)) using (MemoryStream responseInMemory = new MemoryStream()) { await response.CopyToAsync(responseInMemory); data = responseInMemory.ToArray(); } BeginInvokeOnMainThread(delegate { using ( NSData imageData = NSData.FromArray(data) ) { using ( UIImage image = new UIImage(imageData) ) { this.ImageView.Image = image; } } }); http://bit.ly/ 1ukw1ii
40. byte[] data = null; using (Stream response = await session.DownloadResourceAsync(request)) using (MemoryStream responseInMemory = new MemoryStream()) { await response.CopyToAsync(responseInMemory); data = responseInMemory.ToArray(); } BeginInvokeOnMainThread(delegate { using ( NSData imageData = NSData.FromArray(data) ) { using ( UIImage image = new UIImage(imageData) ) { this.ImageView.Image = image; } } }); http://bit.ly/ 1ukw1ii
41. byte[] data = null; using (Stream response = await session.DownloadResourceAsync(request)) using (MemoryStream responseInMemory = new MemoryStream()) { await response.CopyToAsync(responseInMemory); data = responseInMemory.ToArray(); } BeginInvokeOnMainThread(delegate { using ( NSData imageData = NSData.FromArray(data) ) { using ( UIImage image = new UIImage(imageData) ) { this.ImageView.Image = image; } } }); http://bit.ly/ 1ukw1ii
43. Xamarin.Forms
44. Aiming for a Single Codebase
45. Break their own Principles
46. Unlike other cross-platform mobile frameworks that only offer lowest common denominator experiences through UI abstraction libraries, we make 100% of the iOS and Android APIs available through our native bindings.
48. Per Seat Per Platform
50. Try it!
51. Test on All Platforms
52. Dispose Native Objects Aggressively
53. Build Dedicated GUI for Each Platform
54. Try it!