Get some hints on how to write the code of your iOS apps in a more reusable way. This will make you more efficient and happier.

1. 10 tips for a
reusable
architecture
Jorge D. Ortiz Fuentes
@jdortiz

2. A POWWAU
production

3. Agenda
★Goal
★ Principles
★ Tips
★Q&A

4. Goal

5. Write code that
can be used as
many times & in as
many projects as
possible.

6. Principles

7. SOLID
★ Single Responsibility
★Open/Closed
★ Liskov Substitution
★ Interface Segregation
★Dependency Inversion

8. Tips

9. Forgive me, because
I am going to sin
★ The following are tips, not rules.
★ They might not apply to your code.
★But I would, at least, think about them.

10. 1.

11. Don’t write
reusable code

12. Don’t write start
with reusable
code

13. Don’t start with reusable
code
★ Start with the right idea
★But don’t need the perfect code
★ You can always refactor
★ Shipped is better than perfect

14. 2.

15. But don’t commit
code that is
clearly not
reusable

16. Commit reusable code
★Do the Right Thing™ before committing to
the development branch or any shared
branches.
★Be a good boy scout: If you revisit the
code and it can be improved, do so.

17. 3.

18. Move all the
business logic to
the model

19. Move to the model
★Model > Data
★Business rules
• Behaviors
• Validation
• Importing & exporting
• Migration

20. Instead of
- (IBAction) importPasteText:(id)sender {
UIPasteboard *pasteboard = [UIPasteboard generalPasteboard];
if ([pasteboard containsPasteboardTypes:@[@"public.utf8-plain-text",
@"public.text"]]) {
NSInteger rejectedItems = 0;
CheckItem *newItem = nil;
[self.undoManager beginUndoGrouping];
NSString *textToImport = [pasteboard.string copy];
NSArray *items = [textToImport componentsSeparatedByString:@"n"];
NSUInteger objectNumber = 0;
if ([[self.itemsTableViewDataSource.fetchedResultsController sections] count] > 0) {
id <NSFetchedResultsSectionInfo> sectionInfo =
[self.itemsTableViewDataSource.fetchedResultsController sections][0];
objectNumber = [sectionInfo numberOfObjects];
}
for (NSString *item in items) {
NSArray *itemComponents = [item componentsSeparatedByString:@":"];
NSString *itemName = [itemComponents[0]
stringByTrimmingCharactersInSet:[[NSCharacterSet
alphanumericCharacterSet] invertedSet]];
if ([itemName length] > 0) {
…

21. do
- (IBAction) importPasteText:(id)sender {
UIPasteboard *pasteboard = [UIPasteboard
generalPasteboard];
if ([pasteboard
containsPasteboardTypes:@[@“public.utf8-plain-text",
@"public.text"]]) {
[self.undoManager beginUndoGrouping];
[self.model importItemsInChecklist:
self.checklist fromString:pasteboard.string];
[self.undoManager endUndoGrouping];
}
}

22. 4.

23. Don’t put
presentation logic
into the model

24. Presentation logic
★ It isn’t business logic, but “UI logic”
★ In the VC, it could be inconsistent, better
“centralized”.
★ It shouldn’t be in the model.
★ It can contain UI dependent information
(colors, fonts,…).

25. Instead of
// Set label to “3 days left”
- (void) displayRemainingTime {
self.remainingLabel.text =
[self.task remainingTime];
}

26. do
// Set label to “3 days left”
- (void) displayRemainingTime {
TaskPresenter *tp =
[[TaskPresenter alloc]
initWithTask:self.task];
self.remainingLabel.text = [tp
remainingTime];
}

27. 5.

28. Put the network
closer to the
model (instead of
View Controller)

29. Network code
★ The view controller is responsible for responding events:
• lifecycle
• UI generated
★Controlling networking is OK
★ Doing networking is wrong
★ In the model or a category:
• Provide business logic with network functionality
• Handle concurrency

30. 6.

31. Make classes for
Data Sources &
Delegates of
table views

32. Data Source & Delegate
Objects
★ It exceeds VC responsibilities
★Responsibility: View model
★ They can be reused

33. Instead of
// @interface MyVC:
UITableViewController
@implementation MyVC {
//implicit (in super)
// self.tableView.dataSource = self;
// self.tableView.delegate = self;
}

34. do
// @interface MyVC: UITableViewController
@interface MyVC
@property (strong) MyDataSrc *myDataSrc;
@end
@implementation MyVC
- (void) viewDidLoad {
[self assignDataSource];
}
- (void) assignDataSource {
self.myDataSrc = [[MyDataSrc alloc] initWithMOC:self.moc];
self.myDataSrc.fetchedResourceController.delegate.self;
self.tableView.dataSource = self;
[self.myDataSource performFetch];
}
@end

35. 7.

36. But then, don’t
let them take
care of the views

37. DataSource & Delegate
responsibilities
★Metadata: How many rows, sections…
★ Act on data: add or delete row
★ Provide views, view info and present data
★ Act on selections

38. Use a delegate
numberOfSectionInTableView:
tableView:numberOfRowsInSection:
tableView:cellForRowAtIndexPath:
MyVC MyDataSrc
displayObject:inCell

39. TableViewViewModelDele
gate
@protocol TableViewViewModelDelegate <NSObject>
- (NSString *) cellIdentifier;
- (CGFloat) cellHeight;
- (UITableViewCell *) displayObject:(NSManagedObject *)object
inCell:(UITableViewCell *)cell;
- (NSString *) headerIdentifier;
- (CGFloat) headerHeight;
- (UITableViewHeaderFooterView *) displayObject:(NSManagedObject
*)object
inHeader:
(UITableViewHeaderFooterView *)header;
@optional
- (void) didSelectObject:(NSManagedObject *)object;
- (void) didSelectAccessoryForObject:(NSManagedObject *)object;
@end

40. 8.

41. Test your code

42. Test
★Reusable code = code + tests
★ Tests contain
• Validation
• Assumptions
• Documentation

43. Test your Core Data
model
@implementation CoreDataTestCase
- (void) setUp {
[super setUp];
[self createCoreDataStack];
}
- (void) createCoreDataStack {
NSBundle *bundle = [NSBundle bundleForClass:[self class]];
model = [NSManagedObjectModel mergedModelFromBundles:@[bundle]];
coordinator = [[NSPersistentStoreCoordinator alloc]
initWithManagedObjectModel:model];
store = [coordinator addPersistentStoreWithType: NSInMemoryStoreType
configuration: nil
URL: nil
options: nil
error: NULL];
context = [[NSManagedObjectContext alloc]
initWithConcurrencyType:NSMainQueueConcurrencyType];
context.persistentStoreCoordinator = coordinator;
}

44. Test your view controllers
- (void) setUp {
[super setUp];
[self createFixture];
[self createSut];
}
- (void) createSut {
UIStoryboard *storyboard = [UIStoryboard
storyboardWithName:storyboardName bundle:nil];
sut = [storyboard
instantiateViewControllerWithIdentifier:viewControllerID];
sut.data = data;
}

45. Test your view controllers
(2)
- (void)
testOnViewDidLoadTitleIsSetToChecklistName {
[sut view];
XCTAssertTrue([sut.title
isEqualToString:sut.checklist.name],
@"View controller title must be
set to the checklist name");
}

46. 9.

47. Break up your
Storyboards into
workflows

48. Huge Storyboards
Something to avoid

49. Workflows
★Huge Storyboards:
• Teams get conflicts in the Storyboards often
• Difficult to maintain
★Better Storyboards:
• One per workflow (sign in/sign up, statistics,
preferences)
• Even combine with XIB (useful for cells)

50. Load another Storyboard
- (IBAction) displayReport:(id)sender {
UIViewController *reportVC =
[[UIStoryboard
storyboardWithName:reportStoryboard
bundle:nil]
instantiateInitialViewController];
[self presentViewController:reportVC
animated:YES
completion:nil];
}

51. 10.

52. Create your own
modules

53. Modular code
★ iOS support
• Until iOS 8: only static libraries (no
resources, separated headers)
• iOS 8: frameworks
★Cocoapods: allow to share open source
code

54. Create a pod
★ Isolate the code (use pod-template)
★Create .podspec & LICENSE
★ pod lib create coolpod
★ In your Podfile:
• pod ‘coolpod', :git => 'https://
server/repoURL/coolpod.git'

55. Thank
you! Images courtesy of Shutterstock