Lighter View Controllers

Talk at Cocoaheads.nl

(Architecture image by Manu Cornet)

Transcript

1. Lighter View Controllers Chris Eidhof CocoaHeads NL
2. MVC Model View Controller
3. MVC Model View Controller Massive View Controller
5. What's the largest file? find . -name "*.m" -exec wc -l "{}" \; | sort -n
6. Steps Project: A complete OS in < 20K lines
7. View Controllers are the least reusable part
8. A view controller intermediates between model and view
9. Model logic
10. View logic
11. View layout
12. Web Service
13. Too much already?
14. Delegates
15. IBActions ?
16. Pragma marks ??
18. Child View Controllers
19. Table View Controllers ☆ Editing Mode ☆ Keyboard notifications ☆ Flashing scroll indicators ☆ Clearing Selection ☆ Pull to Refresh
22. View Controller Transitions
24. Pulling out protocols
25. For example: UITableViewDataSource
26. Creating a separate data source object @interface FetchedResultsControllerDataSource : NSObject <UITableViewDataSource, NSFetchedResultsControllerDelegate>
27. Creating a separate data source object - (NSInteger)numberOfSectionsInTableView:(UITableView*)t { return self.fetchedResultsController.sections.count; }
28. Creating a separate data source object - (NSInteger)tableView:(UITableView*)tableView numberOfRowsInSection:(NSInteger)sectionIndex { id<NSFetchedResultsSectionInfo> section; section = self.frc.sections[sectionIndex]; return section.numberOfObjects; }
29. Creating a separate data source object Working with the delegate - (UITableViewCell*)tableView:(UITableView*)tv cellForRowAtIndexPath:(NSIndexPath*)ip { id object = [self objectAtIndexPath:indexPath]; id cell = [tv dequeueReusableCellWithIdentifier:ruI forIndexPath:ip]; [self.delegate configureCell:cell withObject:object]; return cell; }
30. Advantages of a separate data source ☆ Lighter view controller ☆ Testable ☆ Reusable And you can do this for other protocols, too...
31. A separate data source ☆ NSArrayDataSource ☆ NSFRCollectionViewController ☆ ...
32. Categories
33. Configuring a cell - (UITableViewCell*)tableView:(UITableView*)tv cellForRowAtIndexPath:(NSIndexPath*)ip { PhotoCell *cell = [tableView dequeueReusableCellWithIdentifier:@"PhotoCell"]; Photo *photo = [self itemAtIndexPath:indexPath]; cell.photoTitleLabel.text = photo.name; NSString* date = [self.dateFormatter stringFromDate:photo.creationDate]; cell.photoDateLabel.text = date; }
34. Configuring a cell Pulling out the reusable part @implementation PhotoCell (ConfigureForPhoto) - (void)configureForPhoto:(Photo *)photo { self.photoTitleLabel.text = photo.name; NSString* date = [self.dateFormatter stringFromDate:photo.creationDate]; self.photoDateLabel.text = date; } @end
35. Configuring a cell The refactored delegate method - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { PhotoCell *cell = [tableView dequeueReusableCellWithIdentifier:PhotoCellIdentifier]; [cell configureForPhoto:[self itemAtIndexPath:indexPath]]; return cell; }
36. Using Interface Builder
38. Intentions
39. Intentions View Controllers may only contain code that effects view changes in response to data changes. Source: http://bendyworks.com/geekville/articles/ 2014/2/single-responsibility-principle-ios
40. Intentions The IBAction macro must not be used in a View Controller
41. Intentions The @interface block in a View Controller's header file must be blank.
42. Intentions A View Controller may not implement any extra *Delegate or *DataSource protocols except for observing Model changes.
43. Intentions A View Controller may only do work in viewDidLoad (or awakeFromNib), viewDidAppear, viewDidDisappear, and in response to an observed change in the model layer.
45. Testing
46. Testing View controllers are notoriously hard to test → Make them light.
47. Commercial Break
50. Questions? @chriseidhof