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Andrei Raifura iOS Department Manager, YOPESO
#CodeWăy
UIViewController: Fighting the monster
Overview
• The “monster” problem
• A practical solution
• View Controllers from historical perspective
Historical approach
Historical approach
Historical approach
Meet UIViewController
• Contains the View
• Manages the View
• Plays well with Interface Builder
• Defines a screen
• Conforms to MVC
Conceptual MVC
Model View
Controller
UpdateUpdate
User ActionNotify
ViewController’s MVC
Model ViewControllerView
Update
Notify
Meet UIViewController
The problem
Things changed
ViewController is the same (almost)
Model ViewControllerView
Update
Notify
ViewController’s Responsibilities
• View layout
• View management code
• Navigation logic
• View setup
• Core Data and NSFetchedResultsController code
• Delegate methods
• Other “decision making” code
View setup
@interface FMViewController () @property (weak, nonatomic) IBOutlet UITextField *usernameTextField; @property (weak, nonatomic) IBOutlet UITextField *passwordTextField; @property (weak, nonatomic) IBOutlet UIView *feedbackView; @property (weak, nonatomic) IBOutlet UIActivityIndicatorView *activityIndicator;
@end
@implementation FMViewController
View setup
- (void)viewDidLoad { [super viewDidLoad]; self.myButton.titleLabel.font = myCustomFont; UIImage *stretchableImage = [self.myButton setBackgroundImage:stretchableImage forControlState:UIControlStateNormal]; }
ViewController’s Responsibilities
• View layout
• View management code
• Navigation logic
• View setup
• Core Data and NSFetchedResultsController code
• Delegate methods
• Other “decision making” code
View layout
- (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; self.myLabel.frame = /* ... */ self.myButton.frame = /* ... */ }
View layout
ViewController’s Responsibilities
• View layout
• View management code
• Navigation logic
• View setup
• Core Data and NSFetchedResultsController code
• Delegate methods
• Other “decision making” code
ViewController’s Responsibilities
• View layout
• View management code
• Navigation logic
• View setup
• Core Data and NSFetchedResultsController code
• Delegate methods
• Other “decision making” code
Navigation logic
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { id item = [self itemAtIndexPath:indexPath]; DetailsViewController *detailsVC = [[DetailsViewController alloc] initWithItem:item]; [self.navigationController pushViewController:detailsVC animated:YES]; }
ViewController’s Responsibilities
• View layout
• View management code
• Navigation logic
• View setup
• Core Data and NSFetchedResultsController code
• Delegate methods
• Other “decision making” code
Core Data code
• View layout
• View management code
• Navigation logic
• View setup
• Core Data and NSFetchedResultsController code
• Delegate methods
• Other “decision making” code
ViewController’s Responsibilities
• View layout
• View management code
• Navigation logic
• View setup
• Core Data and NSFetchedResultsController code
• Delegate methods
• Other “decision making” code
ViewController’s Responsibilities
• View layout
• View management code
• Navigation logic
• View setup
• Core Data and NSFetchedResultsController code
• Delegate methods
• Other “decision making” code
Decision making code
DetailsViewController *detailsVC = /* ... */; if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) { // display details in the split view controller's // details pane } else { // push details to the current navigation controller }
ViewController’s Responsibilities
• View layout
• View management code
• Navigation logic
• View setup
• Core Data and NSFetchedResultsController code
• Delegate methods
• Other “decision making” code
iOS Architecture
Looking into a View Controller
Looking for a solution
ViewController’s Responsibilities
• View layout
• View management code
• Navigation logic
• View setup
• Core Data and NSFetchedResultsController code
• Delegate methods
• Other “decision making” code
ViewController’s Responsibilities
• View layout
• View management code
• Navigation logic
• View setup
• Core Data and NSFetchedResultsController code
• Delegate methods
• Other “decision making” code
Demo
Reduced Responsibilities
• View layout
• View management code
• View setup
View Controller issues
• Cannot be tested (using unit tests)
• Requires changes when the UI is changed
ViewController’s MVC
Model ViewControllerView
Update
Notify
ViewController’s MVC
ViewControllerView
ViewController’s MVC
ViewController ViewUpdate
User Action
Demo
• Use View Models to encapsulate the information the view displays
• Put the IBOutlets in the private interface
• Create classes for views
• Use XIBs to define your layout
• Use a delegate to communicate asynchronous events from the view
• View keeps the datasources
Separate View from View Controller
• Testable View Controllers
• Ability to change the View without touching the View Controller
• More granular code
• It plays well with MVVM and VIPER concepts
Advantages
• Cannot use storyboards
• May lead to class explosion
• Requires some glue code
Disadvantages
One more thing?
Summary
• The “monster” problem
• A practical solution
• View Controllers from historical perspective
Questions?
Contacts
Raifura Andrei iOS Department Manager, YOPESO
#CodeWăy
