Lighter View Controllers

Mobile Warsaw edition. Including Ultra Light View Controllers.

Transcript

1. Lighter View Controllers Chris Eidhof Mobile Warsaw
2. Android People » View Controller 㲗 Activity » Protocol 㲗 Interface
3. What is the largest file in your project?
5. ⾠ “My point isn’t that it’s never a good idea to break up a large view controller. My point is that it’s worth noticing when it’s not actually helping, when it’s adding complexity - and that it’s worth finding the right balance, which takes some thinking.” Brent Simmons
6. MVC
7. Massive View Controller
8. MVC » Model code in model » View-related code in view (or IB) » Webservice in service layer
9. Model code in model - (void)loadPriorities { NSDate* now = [NSDate date]; NSString* formatString = @"startDate <= %@ AND endDate >= %@"; NSPredicate* predicate = [NSPredicate predicateWithFormat:formatString, now, now]; NSSet* priorities = [self.user.priorities filteredSetUsingPredicate:predicate]; self.priorities = [priorities allObjects]; }
10. Model code in model - (void)loadPriorities { self.priorities = [user currentPriorities]; }
11. MCE Recap
12. Limit your file size
13. Pull out methods
14. Use categories to populate views
15. Pull out protocols
16. Pull out protocols » UITableViewDataSource » UICollectionViewDataSource » UITextViewDelegate
17. #pragma mark UITextFieldDelegate - (BOOL)textField:(UITextField*)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString*)string { if ([string isEqualToString:@"\n"]) { [textField resignFirstResponder]; return NO; } return YES; }
18. A possible problem This might introduce a lot of extra glue code.
19. Frameworks » Use the frameworks » Child View Controllers » View Controller Transitions for state » Optimize your VC for testability
20. UITableViewController “When the table view is about to appear the first time it’s loaded, the table- view controller reloads the table view’s data. It also clears its selection every time the table view is displayed.” UITableViewController Class Reference
21. UITableViewController “When the table view has appeared, the controller flashes the table view’s scroll indicators. The UITableViewController class implements this in the superclass method viewDidAppear:.” UITableViewController Class Reference
22. UITableViewController “It implements the superclass method setEditing:animated: so that if a user taps an Edit|Done button in the navigation bar, the controller toggles the edit mode of the table.” UITableViewController Class Reference
23. UITableViewController » Clears selection » Flashes scroll indicators » Editing behavior » Pull to refresh » Keyboard notifications
24. However...
26. View Controller Transitions
29. Ultra Light View Controllers
30. Single Responsibility Principle & iOS http://bendyworks.com/geekville/articles/ 2014/2/single-responsibility-principle- ios
31. The IBAction macro must not be used in a VC
32. The @interface block in a VC's header file must be blank.
33. A VC may not implement any extra *Delegate or *DataSource protocols
34. A VC may only do work in viewDidLoad, viewDidAppear, viewDidDisappear, and in response to an observed change in the model layer.
36. @interface ViewController () <UITextFieldDelegate> @property (weak, nonatomic) IBOutlet UILabel *label; @property (weak, nonatomic) IBOutlet UITextField *textField; @property (nonatomic, strong) Person* person; @end @implementation ViewController - (void)viewDidLoad { [super viewDidLoad]; self.person = [Person new]; self.person.name = @"Chris"; [self updateTextField]; } #pragma mark Actions - (IBAction)reverse:(id)sender { self.person.name = self.textField.text.reversedString; [self updateTextField]; } - (IBAction)uppercase:(id)sender { self.person.name = self.textField.text.uppercaseString; [self updateTextField]; } #pragma mark UITextFieldDelegate - (BOOL)textField:(UITextField*)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString*)string { if ([string isEqualToString:@"\n"]) { [textField resignFirstResponder]; return NO; } return YES; } - (void)updateTextField { self.textField.text = self.person.name; } @end
37. @interface ViewController () <UITextFieldDelegate> @property (weak, nonatomic) IBOutlet UILabel *label; @property (weak, nonatomic) IBOutlet UITextField *textField; @property (nonatomic, strong) Person* person; @end
38. @implementation ViewController - (void)viewDidLoad { [super viewDidLoad]; self.person = [Person new]; self.person.name = @"Chris"; [self updateTextField]; }
39. #pragma mark Actions - (IBAction)reverse:(id)sender { self.person.name = self.textField.text.reversedString; [self updateTextField]; } - (IBAction)uppercase:(id)sender { self.person.name = self.textField.text.uppercaseString; [self updateTextField]; }
40. #pragma mark UITextFieldDelegate - (BOOL)textField:(UITextField*)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString*)string { if ([string isEqualToString:@"\n"]) { [textField resignFirstResponder]; return NO; } return YES; } - (void)updateTextField { self.textField.text = self.person.name; } @end
41. Refactor
42. find . -name '*.m' -exec wc -l {} + | sort -n 13 ./Intentions/AppDelegate.m 13 ./Intentions/ModelContainer.m 13 ./Intentions/Person.m 18 ./Intentions/main.m 19 ./Intentions/ViewController.m 22 ./Intentions/NSString+Reverse.m 26 ./Intentions/DismissOnEnterIntention.m 27 ./Intentions/ReverseIntention.m 27 ./Intentions/UppercaseIntention.m 45 ./Intentions/ObserveIntention.m
43. - (void)viewDidLoad { [super viewDidLoad]; Person *person = [Person new]; person.name = @"Chris"; self.modelContainer.model = person; }
45. @interface UppercaseIntention () @property (weak) IBOutlet UITextField *textField; @property (weak) IBOutlet ModelContainer *modelContainer; @property (copy) NSString *modelKeyPath; @end @implementation UppercaseIntention - (IBAction)capitalize:(id)sender { [self.modelContainer.model setValue:self.textField.text.uppercaseString forKey:self.modelKeyPath]; } @end
48. Plan of Attack 1.Put things into separate methods 2.Group the methods together 3.Move related methods into their own class
49. More reading » http://www.objc.io/issue-1/ » http://bendyworks.com/geekville/ articles/2014/2/single-responsibility- principle-ios » http://blog.securemacprogramming.com/? p=1222
51. Thanks » @chriseidhof » objc.io » uikonf.com » decksetapp.com
52. Credits » The life of a software engineer - Manu Cornet