The base architecture of iOS is MVC (Model View Controller) which leads into known as Massive View Controller, where the View Controllers end up doing so many logic. It is easy to mix UI code and business logic together which is the wrong way to test the logic. VIPER is one of a modern architecture made for this issue. It is based by Uncle Bob's Clean Architecture. It use the Separation of Concern principle which make the code cleaner and easy to maintenance.

1. Introduction to VIPER
Architecture
Hendy Christianto

2. Why VIPER?
• MVC - Massive View Controller
• What goes into View Controllers?
• Data sources for Views (UITableViews)
• Business Logic
• Application Flows
• Transition between view controller

3. What is VIPER?
• Based on clean architecture to Uncle Bob’s
clean architecture.
• Basically a new architecture, introduced on 2014
• Used to resolve “Massive View Controller”
• Using “Single Responsibility” as a principle

4. Architecture of VIPER

5. View
• The View is passive
• Waits for the Presenter to give content to display
• Detect user interaction
• The view is an abstract interface

6. View Cont’d
@protocol SignInEmailView <NSObject>
- (void)setEmailLabelText:(NSString *)email;
- (void)setPasswordLabelText:(NSString *)password;
@end
#import <UIKit/UIKit.h>
#import "SignInEmailView.h"
@interface ViewController : UIViewController <SignInEmailView>
@end
only protocols, abstract interface
implements SignInEmailView interface
View Presenter
setPasswordLabelText:

7. Presenter
• Tells the view what to display
• Handle events

8. Presenter Cont’d
@implementation ViewController
#pragma mark -
#pragma mark View Interface
- (void)setEmailLabelText:(NSString *)email {
self.emailLabel.text = email;
}
- (void)setPasswordLabelText:(NSString *)password {
self.passwordLabel.text = password;
}
- (void)setErrorMessage:(NSString *)error {
self.errorLabel.text = error;
}
#pragma mark -
#pragma mark IBAction
- (IBAction)buttonLoginClicked:(id)sender {
[self.presenter didLoginWithEmail:self.emailTextField.text
password:self.passwordTextField.text];
}
PresenterView
buttonLoginClicked:
didLoginWithEmail: password:
Interactor
signInWithEmail:password:
@implementation SignInPresenter
#pragma mark -
#pragma mark Wireframe Update UI
- (void)presentSignInEmailView {
[self.view setPasswordLabelText:@"Password"];
[self.view setEmailLabelText:@"Email"];
}
- (void)didLoginWithEmail:(NSString *)email password:(NSString *)password {
[self.interactor signInWithEmail:email password:password];
}
@end
#import <Foundation/Foundation.h>
#import "SignInEmailView.h"
#import "SignInInteractorIO.h"
@interface SignInPresenter : NSObject
@property (nonatomic, weak) id <SignInEmailView> view;
@property (nonatomic, strong) id <SignInInteractorInput> interactor;
- (void)presentSignInEmailView;
- (void)didLoginWithEmail:(NSString *)email password:(NSString *)password;
@end

9. Interactor
• Perform business logic
• Carry out events that notified by presenter
(input)
• Produce output and notify back the presenter

10. Interactor Cont’d
InteractorPresenter
signInWithEmail:password:
didSignInWithResponse:
@implementation SignInPresenter
#pragma mark -
#pragma mark Wireframe Update UI
- (void)presentSignInEmailView {
[self.view setPasswordLabelText:@"Password"];
[self.view setEmailLabelText:@"Email"];
}
- (void)didLoginWithEmail:(NSString *)email password:(NSString *)password {
[self.interactor signInWithEmail:email password:password];
}
#pragma mark -
#pragma mark Interactor
- (void)didSignInWithResponse:(NSDictionary *)response {
NSError *error = response[@"error"];
if (error) {
[self.view setErrorMessage:error.domain];
} else {
[self.signInWireframe pushWelcomeView];
}
}
@interface SignInInteractor ()
@property (nonatomic, strong) SignInDataManager *dataManager;
@end
@implementation SignInInteractor
- (void)signInWithEmail:(NSString *)email password:(NSString *)password {
[self.dataManager userWithEmail:email password:password completion:^(User *user) {
NSMutableDictionary *response = [NSMutableDictionary new];
if (user) {
response[@"user"] = user;
} else {
response[@"error"] = [NSError errorWithDomain:@"User Not Found"
code:404 userInfo:nil];
}
[self.output didSignInWithResponse:response];
}];
}
@end
@interface SignInInteractor : NSObject <SignInInteractorInput>
@property (nonatomic, weak) id <SignInInteractorOutput> output;
@end
@protocol SignInInteractorInput <NSObject>
- (void)signInWithEmail:(NSString *)email password:(NSString *)password;
@end
@protocol SignInInteractorOutput <NSObject>
- (void)didSignInWithResponse:(NSDictionary *)response;
Data
Manager
userWithEmail:password:completion:
completion:^(User *user)

11. Data Manager
• Fetch data from database
• Restructure data to model / entities
• Store data

12. Data Manager Cont’d
Data
Manager
Interactor
@interface SignInInteractor ()
@property (nonatomic, strong) SignInDataManager *dataManager;
@end
@implementation SignInInteractor
- (void)signInWithEmail:(NSString *)email password:(NSString *)password {
[self.dataManager userWithEmail:email password:password completion:^(User *user) {
NSMutableDictionary *response = [NSMutableDictionary new];
if (user) {
response[@"user"] = user;
} else {
response[@"error"] = [NSError errorWithDomain:@"User Not Found"
code:404 userInfo:nil];
}
[self.output didSignInWithResponse:response];
}];
}
@end
Service
userWithEmail:password:completion:
@implementation SignInDataManager
- (void)userWithEmail:(NSString *)email password:(NSString *)password
completion:(void (^)(User *))completionBlock {
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(email == %@)", email];
[self.dataStore fetchEntriesWithPredicate:predicate sortDescriptors:@[]
completionBlock:^(NSArray *results) {
if (completionBlock) {
if (results.count == 0) {
completionBlock(nil);
} else {
completionBlock(results[0]);
}
}
}];
}
@end
fetchEntriesWithPredicate:sortDescriptors:completionBlock
results arrayrun completionBlock:

13. Service
• Execute requests related to Entities / Models
• Network/ API, Database (local)

14. Entities
• Represent data
• Passed between class

15. Entities Cont’d
@interface User : NSManagedObject
@property (nonatomic, strong) NSString *email;
@property (nonatomic, strong) NSString *name;
@end
@implementation User
@dynamic name;
@dynamic email;
@end

16. Wireframe
• Initialize view controllers, Presenter, Interactor
• Handles routing / navigation within Views

17. Wireframe Cont’d
@class SignInPresenter;
@class WelcomeWireframe;
@interface SignInWireframe : RootWireframe
@property (nonatomic, strong) WelcomeWireframe *welcomeWireframe;
- (void)pushWelcomeView;
- (void)presentSignInViewControllerOnWindow:(UIWindow *)window;
@end
static NSString *ViewControllerIdentifier = @"ViewController";
@interface SignInWireframe ()
@property (nonatomic, strong) SignInPresenter *presenter;
@property (nonatomic, strong) SignInInteractor *interactor;
@end
@implementation SignInWireframe
- (void)initializeClasses {
self.presenter = [[SignInPresenter alloc] init];
self.interactor = [[SignInInteractor alloc] init];
self.presenter.interactor = self.interactor;
self.interactor.output = self.presenter;
}
- (void)presentSignInViewControllerOnWindow:(UIWindow *)window {
[self initializeClasses];
ViewController *signInVC = [self signInViewController];
signInVC.presenter = self.presenter;
self.presenter.view = signInVC;
[self createNavigationControllerWithRootView:signInVC];
window.rootViewController = self.navigationController;
}
- (void)pushWelcomeView {
[self.welcomeWireframe pushWelcomeViewControllerOnNavigation:self.navigationController];
}
- (ViewController *)signInViewController {
UIStoryboard *storyboard = [self mainStoryboard];
ViewController *signInVC = [storyboard instantiateViewControllerWithIdentifier:ViewControllerIdentifier];
return signInVC;
}

18. Benefits of Viper
• Easy to iterate on
• Collaboration-friendly
• Separated concerns
• Easy to test

19. Conclusion
• Helps developer to be more explicit about
separation of code
• Single responsibility each class, easier to
maintain
• Neat Code!!

20. References
• http://mutualmobile.github.io/blog/2013/12/04/viper-
introduction/
• http://www.objc.io/issue-13/viper.html
• https://medium.com/brigade-engineering/brigades-
experience-using-an-mvc-alternative-36ef1601a41f
• http://blog.8thlight.com/uncle-bob/2012/08/13/the-clean-
architecture.html
• iOS viper presentation - http://www.slideshare.net/
RajatDatta1/i-os-viper-presentation

21. DEMOS

22. Q&A