1.
Nome
Speaker@twitter
MVP vs MVVM
a fast introduction

2.
● We are talking about GUIs
Why?
BECAUSE IT’S HARD TO TEST
YOUR GUI !
● GUIs consist of widgets that contain the state of the GUI screen
● Most rich client frameworks encourage putting presentation behavior in
the view class
● Most rich client framework were not build with automated testing in mind

3.
Acronyms
MVP: Model View Presenter
MVVM: Model View ViewModel

4.
Model
● This is the data upon which the user interface will operate.
● It’s purely a domain object and there is no expectation of (or link to) the
user interface at all.
● The intention is that such objects should have no knowledge of the user
interface.
● You can test it in isolation!

5.
(Humble) View
● The view is a humble object:
○ any object that is difficult to test should have minimal behavior.
● Reduce the behavior of the UI components to the absolute minimum
● The view is a dumb slave of the controller:
○ forwards user events to the controller
○ widget updates are pushed by the controller
● Make the view sufficiently humble to help in testing
○ you run little risk by not testing the view
○ if we are unable to include it in our test suites we minimize the
chances of an undetected failure

6.
● It updates the model, and then handles the reloading of the view.
● Easily testable using test double without needing any interaction with
the UI framework
MVP - Presenter
● It receives all user events
○ the view is a dependency of the Presenter
○ data are pulled from the model, and using them to update the
widgets

7.
● It leaves to the view to synchronize all its updates
● It stores the view state (only the once that can change)
MVVM - ViewModel
● It receives all user events
○ abstraction of the view that is not dependent on a specific GUI
framework
○ The view is not a dependency
○ It provides an interface to the view
■ mainly using the observer pattern and data binding

8.
References
● https://www.martinfowler.com/eaaDev/uiArchs.html
● https://martinfowler.com/eaaDev/PassiveScreen.html
● https://martinfowler.com/eaaDev/SupervisingPresenter.html
● https://martinfowler.com/eaaDev/PresentationModel.html
● http://www.object-
arts.com/downloads/papers/TwistingTheTriad.PDF

9.
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