iOS design patterns: MVC, MVP and MVVM

Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved.Copyright ©2016 Talentica Software (I) Pvt Ltd. All rights reserved. 2 Agenda • Separation of Concerns • MVC • Problems with MVC • MVP • MVVM • Working MVVM App

Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved.Copyright ©2016 Talentica Software (I) Pvt Ltd. All rights reserved. 3 Separation of concerns • In computer science, separation of concerns (SoC) is a design principle for separating a computer program into distinct sections, such that each section addresses a separate concern. • When concerns are well-separated, individual sections can be reused, as well as developed and updated independently.

Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved.Copyright ©2016 Talentica Software (I) Pvt Ltd. All rights reserved. 4 M-V-C (Model View Controller) • A proven pattern for organizing your code in complex application design, also the Apple recommended way of programming an app. • It’s also proven to have a second meaning in iOS development: Massive View Controller. • Apple hasn’t provided any real guidance on how to solve the Massive View Controller problem

Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved.Copyright ©2016 Talentica Software (I) Pvt Ltd. All rights reserved. 7 Apple’s MVC Code: var userCell = tableView.dequeueReusableCellWithIdentifier("identifier") as UserCell userCell.configureWithUser(user)

Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved.Copyright ©2016 Talentica Software (I) Pvt Ltd. All rights reserved. 8 Problems with MVC • Distribution— the View and the Model in fact separated, but the View and the Controller are tightly coupled. • Testability — due to the bad distribution you’ll probably only test your Model. • Ease of use — the least amount of code among others patterns. In addition everyone is familiar with it, thus, it’s easily maintained even by the inexperienced developers.

Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved.Copyright ©2016 Talentica Software (I) Pvt Ltd. All rights reserved. 12 MVP- Features • Distribution — we have the most of responsibilities divided between the Presenter and the Model, with the pretty dumb View • Testability — is excellent, we can test most of the business logic due to the dumb View. • Easy of use — in our simple example, the amount of code is doubled compared to the MVC, but at the same time, idea of the MVP is very clear.

Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved.Copyright ©2016 Talentica Software (I) Pvt Ltd. All rights reserved. 15 Some rules of MVVM • The View has a reference to the ViewModel, but not vice-versa. • The ViewModel has a reference to the Model, but not vice-versa. • Business logic controller(VM) should have no reference of UIKit. • View should be only responsible for UI handling. • View should not interact with Data Model or vice-versa. • View Model is responsible only for processing input to output and logic required for driving the UI as in demo example.

Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved.Copyright ©2016 Talentica Software (I) Pvt Ltd. All rights reserved. 16 MVVM-Features • Distribution —MVVM’s View has more responsibilities than the MVP’s View. • Testability— the View Model knows nothing about the View, this allows us to test it easily. • Easy of use — its has the same amount of code as the MVP in our example, but MVVM would be much skinnier if you used bindings.[ReactiveCocoa]

Copyright © 2016 Talentica Software (I) Pvt Ltd. All rights reserved.Copyright ©2016 Talentica Software (I) Pvt Ltd. All rights reserved. 18 References • https://academy.realm.io/posts/krzysztof-zablocki-mDevCamp-ios- architecture-mvvm-mvc-viper/ • https://github.com/blkbrds/arch-mvvm-ios (Remove the lint pod from podfile and build phases to make the project run) • The references of the all the patterns are available on Github:https://github.com/suyashgupta25/iOSPatternsSamples

iOS design patterns: MVC, MVP and MVVM

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