Mobile architecture problems and solutions.

1. Mobile Architecture
Chris Jimenez

2. Mobile Architecture
En el principio de los tiempos...

3. MVC

4. Cons
◦ Massive View Controller!
◦ Sometimes hard to test
◦ More “layers” are needed as app
grows
◦ Its an “Apple thing”
◦ Decrease code clarity
◦ There are better design
patterns

5. What better you say?
MVVM - Model View View Model
--iOS
MVP - Model View Presenter
--Android

6. MVVM
◦ View controllers are technically
distinct components, they
almost always go hand-in-hand
together, paired
◦ When is the last time that a
view could be paired with
different view controllers??

7. MVVM
So why not formalize their
connection?

8. MVVM
◦ Most of the stuff in
ViewController is presentation
logic
◦ Things like transforming values
from the model into something
the view can present

9. MVVM
MVVM to the rescue

10. MVVM
MVVM is an augmented version of
MVC where we formally connect
the view and controller, and move
presentation logic out of the
controller and into a new object.

11. MVVM
Why?
◦ Reduces the complexity of one’s
view controllers and makes
one’s presentation logic easier
to test

12. Some Code
@interface Person : NSObject
- (instancetype)initwithSalutation:(NSString *)salutation firstName:(NSString
*)firstName lastName:(NSString *)lastName birthdate:(NSDate *)birthdate;
@property (nonatomic, readonly) NSString *salutation;
@property (nonatomic, readonly) NSString *firstName;
@property (nonatomic, readonly) NSString *lastName;
@property (nonatomic, readonly) NSDate *birthdate;
@end

13. PersonViewController.m
- (void)viewDidLoad {
[super viewDidLoad];
if (self.model.salutation.length > 0) {
self.nameLabel.text = [NSString stringWithFormat:@"%@ %@ %@", self.model.salutation,
self.model.firstName, self.model.lastName];
} else {
self.nameLabel.text = [NSString stringWithFormat:@"%@ %@", self.model.firstName,
self.model.lastName];
}
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"EEEE MMMM d, yyyy"];
self.birthdateLabel.text = [dateFormatter stringFromDate:model.birthdate];
}

14. Now with MVVM, PersonViewModel.h
@interface PersonViewModel : NSObject
- (instancetype)initWithPerson:(Person *)person;
@property (nonatomic, readonly) Person *person;
@property (nonatomic, readonly) NSString *nameText;
@property (nonatomic, readonly) NSString *birthdateText;
@end

15. PersonViewModel.m
@implementation PersonViewModel
- (instancetype)initWithPerson:(Person *)person {
self = [super init];
if (!self) return nil;
_person = person;
if (person.salutation.length > 0) {
_nameText = [NSString stringWithFormat:@"%@ %@ %@", self.person.salutation,
self.person.firstName, self.person.lastName];
} else {
_nameText = [NSString stringWithFormat:@"%@ %@", self.person.firstName,
self.person.lastName];
}

16. An our view controller
- (void)viewDidLoad {
[super viewDidLoad];
self.nameLabel.text = self.viewModel.nameText;
self.birthdateLabel.text = self.viewModel.birthdateText;
}

17. MVVM
Chiva!

18. MVP Model View Presenter
Presenter is a layer that provides
View with data from Model.
Presenter also handles
background tasks.

19. Why?
◦ Keep it stupid simple
◦ Removes complexity
◦ Easy to test

20. Normal View Model in Android

21. On top of that
◦ View can disappear and appear
at random time
◦ Do not forget about
saving/restoring of Views
◦ Attach a couple of background
tasks to that temporary Views

22. Model View Presenter

23. MVP Pros
◦ Complex tasks are split into
simpler tasks and are easier to
solve.
◦ Smaller objects, less bugs,
easier to debug.
◦ Testable.

24. MVP Background Tasks
Background Tasks

25. Code time