Whats MVVMC?

1. iOS: MVVMC
MobileMonday
15 May 2017
Aleksandr Nikolajev
iOS developer

2. ME
• Graduated as material scientist in University of
Tartu
• Joined Mooncascade in 2015
• FinTech, transportation, multimedia, sports,
utilities

3. AGENDA
• Introduction to MVVMC and it’s pieces
• Some examples
• Unit testing

4. • Tight coupling between View and Controller
• Hard to test interactions between View and
Controller
• Model can be testable
THE PROBLEM WITH
APPLE’s MVC

5. • An architecture pattern
• Model - View - ViewModel - Coordinator
• MVVMC treats UIViewController as a dumb
presenter - just a view
WHAT IS MVVMC ?

6. HOW IT WORKS ?
• Coordinator - owns View and/or another Coordinator(s), notifies Coordinator(s)
• View - owns ViewModel, notifies ViewModel (e.g button tap)
• ViewModel - owns Model, updates View, notifies Coordinator

7. Model
• Usually a protocol
• C.R.U.D - Create, Read, Update, Delete
• Uses functions, NOT properties
• Injected into ViewModel

9. ViewModel
• Usually a class
• Independent of UIKit
• Injected into View and has no idea what the View is
• Business logic
• Operate with Model
• Provide presentation data to view and notify if that data has
changed
• Communicate states to Coordinator

11. Coordinator
• Declared as a protocol
• Handle navigation
• Create View and inject ViewModel into it

13. COMPLEX FLOWS
• Many UIViewControllers
• Many options to choose where to go
• Does the UIViewController has to know what to
show next?

16. View
• UIViewController is also a View !!!
• Present human readable data
• Do the layout
• Inform ViewModel about interactions

18. NOT ONLY UIViewController
• There is no rule about using ViewModels only
with UIViewController
• You can use ViewModels on almost on every UI
element
• UITextField, UIButton, …

19. NOT ONLY UIViewController
• This will decrease your code lines in ViewModel
• Makes code more distributed and increases
reusability
• Adds more flexibility to write unit tests

22. HOW IT COMES
TOGETHER?
• The GOD — AppCoordinator
• Only AppDelegate knows about AppCoordinator
• Desides what to show when app is finished
launching

25. UNIT TESTING
• ViewModel gets notified about events happened
in the view - we can test what is the result
• Test if presentation data is formatted correctly (e.g
convert Date object into formatted date string)
• Test if correct delegate method is called when it’s
needed to move on with the flow
• Test if errors are shown to view

26. • Well distributed code
• Good testability
• Easy of use
THE PROFIT

27. • MVVM-C A simple way to navigate
http://tech.trivago.com/2016/08/26/mvvm-c-a-
simple-way-to-navigate
• iOS Architecture Patterns
https://medium.com/ios-os-x-development/ios-
architecture-patterns-ecba4c38de52
REFERENCES

28. THANK YOU!

29. If you wish to play with the code, clone this
repo
https://github.com/sasnik/MoMoMVVMC