Lighter View Controllers

Transcript

1. Lighter View Controllers Chris Eidhof CocoaHeads NL

2. MVC Model View Controller

3. MVC Model View Controller Massive View Controller

4. None

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 ??

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18. Child View Controllers

19. Table View Controllers ☆ Editing Mode ☆ Keyboard notifications ☆

    Flashing scroll indicators ☆ Clearing Selection ☆ Pull to Refresh
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22. View Controller Transitions

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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

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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.
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45. Testing

46. Testing View controllers are notoriously hard to test → Make

    them light.

47. Commercial Break

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50. Questions? @chriseidhof