iOS: MVVMC

MobileMonday 15 May 2017

Aleksandr Nikolajev iOS developer

ME• Graduated as material scientist in University of

Tartu

• Joined Mooncascade in 2015

• FinTech, transportation, multimedia, sports, utilities

AGENDA• Introduction to MVVMC and it’s pieces

• Some examples

• Unit testing

• Tight coupling between View and Controller

• Hard to test interactions between View and Controller

• Model can be testable

THE PROBLEM WITH APPLE’s MVC

• An architecture pattern

• Model - View - ViewModel - Coordinator

• MVVMC treats UIViewController as a dumb presenter - just a view

WHAT IS MVVMC ?

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

Model• Usually a protocol

• C.R.U.D - Create, Read, Update, Delete

• Uses functions, NOT properties

• Injected into ViewModel

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

Coordinator• Declared as a protocol

• Handle navigation

• Create View and inject ViewModel into it

COMPLEX FLOWS• Many UIViewControllers

• Many options to choose where to go

• Does the UIViewController has to know what to show next?

View• UIViewController is also a View !!!

• Present human readable data

• Do the layout

• Inform ViewModel about interactions

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, …

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

HOW IT COMES TOGETHER?

• The GOD — AppCoordinator

• Only AppDelegate knows about AppCoordinator

• Desides what to show when app is finished launching

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

• Well distributed code

• Good testability

• Easy of use

THE PROFIT

• MVVM-C A simple way to navigate http://tech.trivago.com/2016/08/26/mvvm-c-a-simple-way-to-navigate

• iOS Architecture Patternshttps://medium.com/ios-os-x-development/ios-architecture-patterns-ecba4c38de52

REFERENCES

THANK YOU!

If you wish to play with the code, clone this repo

https://github.com/sasnik/MoMoMVVMC