Good Intentions: A Path to Better View Controllers

Originally presented at 360iDev in Denver, CO on August 25, 2014

When building iOS apps within the traditional MVC framework, View Controllers unfortunately bear the brunt of being the de facto dumping ground for all manner of disparate functionality. As a result, they are often the biggest and most convoluted files within our iOS projects.

But it doesn’t have to be that way. In this session, we will learn how to unburden our View Controllers by applying the Single Responsibility Principle and delegation through functional Intentions. We’ll find that by adopting the principles of “Lighter” View Controllers our code becomes much more robust to change, yet remains easy to maintain and test.

Transcript

1. Good Intentions A Path to Building Better ViewControllers Jay Thrash @jaythrash ! 360iDev, Denver August 2014
2. We need to talk…
3. Model View Controller
4. Massive View Controller
5. View Controller Misused
6. View Controller Mistreated
7. Delegate (v) Delegate (n)
8. I need _______________________ a DataSource for this TableView ViewController A day in the Life
9. I need _______________________ data fetched from the server ViewController A day in the Life
10. I need _______________________ someone to validate the form fields ViewController A day in the Life
11. I need _______________________ a CLLocationManagerDelegate ViewController A day in the Life
12. I need _______________________ just one more thing. It’s wafer thin. ViewController A day in the Life
13. It’s too much
14. It’s too much We can do better
15. Separation of Concerns Single Responsibility Principal Apply Two Principals
16. Stores Techniques 3 Delegate(v) the DataSources Intentions
17. Stores Encapsulates access to external sources of data.
18. Stores Encapsulates access to external sources of data. Manage Shared Resources ➡ Data Loading & Caching ➡ System Resources ➡ Network ➡ Location ➡ Motion Services ➡ Camera
19. Stores #import <Foundation/Foundation.h> @class MJTLocation; @interface MJTLocationStore : NSObject + (MJTLocationStore *)store; - (MJTLocation *)locationById:(NSString*)locationId; @end
20. Stores #import <Foundation/Foundation.h> @class MJTLocation; @interface MJTLocationStore : NSObject + (MJTLocationStore *)store; - (MJTLocation *)locationById:(NSString*)locationId; @end loc = [[MJTLocationStore store] locationById:id];
21. Stores Candidates for Stores ! ➡Web Services ➡Databases ➡Filesystem ➡Location/Motion Services ➡Camera
22. Delegate the DataSources
23. “Lighter View Controllers” obj.io Issue #1 ! ➡ Remove UITableViewDataSource responsibilities from ViewController ! ➡ Encapsulate into own class Delegate the DataSources
24. Delegate the DataSources -(id)itemAtIndexPath:(NSIndexPath*)indexPath {} -(NSInteger)numberOfSectionsInTableView:(UITableView *)tv -(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section -(UITableViewCell *)tableView:(UITableView *)tv cellForRowAtIndexPath:(NSIndexPath *)indexPath Typical DataSource Pattern
25. Delegate the DataSources -(id)itemAtIndexPath:(NSIndexPath*)indexPath {} ! -(NSInteger)numberOfSectionsInTableView:(UITableView *)tv ! -(NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section ! -(UITableViewCell *)tableView:(UITableView *)tv cellForRowAtIndexPath:(NSIndexPath *)indexPath Typical DataSource Pattern
26. Delegate the DataSources DataSource
27. Backing Store ViewController Delegate the DataSources DataSource
28. Backing Store ViewController Delegate the DataSources DataSource
29. Backing Store ViewController Delegate the DataSources DataSource
30. Backing Store ViewController Delegate the DataSources DataSource @[x, y, z]
31. Backing Store ViewController Delegate the DataSources DataSource @[x, y, z] plist
32. Backing Store ViewController Delegate the DataSources DataSource @[x, y, z] plist CoreData
33. Backing Store ViewController Delegate the DataSources DataSource @[x, y, z] plist CoreData
34. Delegate the DataSources
35. Intentions
36. Intentions UIAlertViewDelegate UITextFieldDelegate UITextFieldDelegate IBOutlets/IBActions
37. Intentions Intention
38. Intentions
39. Intentions Michael ichael-May
40. Intentions @interface ViewController ()<UITextFieldDelegate> @property (strong, nonatomic) IBOutlet UILabel *translatedNameLabel; @property (strong, nonatomic) IBOutlet UITextField *nameTextField; @property (strong, nonatomic) Person *person; @end ViewController
41. Intentions - (void)viewDidLoad { [super viewDidLoad]; self.person = [[Person alloc] init]; [self updateNameLabel]; } -(void)updateNameLabel { self.translatedNameLabel.text = self.person.name; } - (IBAction)convertTapped:(id)sender { self.person.name = self.nameTextField.text.pigLatinizedString; [self updateNameLabel]; } ViewController
42. Intentions - (void)viewDidLoad { [super viewDidLoad]; self.person = [[Person alloc] init]; [self updateNameLabel]; } -(void)updateNameLabel { self.translatedNameLabel.text = self.person.name; } - (IBAction)convertTapped:(id)sender { self.person.name = self.nameTextField.text.pigLatinizedString; [self updateNameLabel]; } ViewController PigLatinIntention
43. Intentions @interface ViewController ()<UITextFieldDelegate> @property (strong, nonatomic) PersonContainer *personContainer; @end - (void)viewDidLoad { [super viewDidLoad]; Person *person = [[Person alloc] init]; self.personContainer.person = person; } ViewController.m
44. Intentions @interface PigLatinIntention () @property (weak, nonatomic) IBOutlet UITextField *textField; @property (weak, nonatomic) IBOutlet UILabel *translatedNameLabel; @property (weak, nonatomic) IBOutlet PersonContainer* personContainer; @end PigLatinIntention.m
45. Intentions @implementation PigLatinIntention - (IBAction)translate:(id)sender { self.personContainer.person.name = self.textField.text.pigLatinizedString; [self updateNameLabel]; } -(void)updateNameLabel { self.translatedNameLabel.text = self.personContainer.person.name; } @end PigLatinIntention.m
46. Intentions
47. Intentions
48. Intentions
49. Intentions
50. Intentions
51. Stores Techniques 3 Delegate(v) the DataSources Intentions
52. Higher Learning Topics to Google ➡ objc.io - Lighter View Controllers
53. Higher Learning Topics to Google ➡ objc.io - Lighter View Controllers ➡ Bendyworks - SRP & iOS ➡ Chris Eidhof - Intentions
54. Thanks! @jaythrash jay@jaythrash.com http://jaythrash.com/talks