Swift interpretation of VIPER

Please keep in mind the objective of Separation of Concern.

Below are described the responsibilities of all layers presents in the VIPER design pattern / architecture:

V for View

The view is responsible for:

• displaying info to the user
• detecting user interaction

The view controller is responsible for:

• holding all attached (IBOutlet) UIView from its storyboard counterpart
• responding to its view-ing protocol
• holding the presenter instance

P for Presenter

The presenter is responsible for:

• holding the interactor instance
• telling the view what to display
• handling user events (such as clicking on a button) and dispatches to the interactor
• act as an integrity checker, before the interactor runs its logic, such as checking for non-empty fields
• does not act as a logic validator, such as checking if the street matches the city

I for Interactor

The interactor is responsible for:

• handling presenter requests
• acting as a logic validator
• interacting with data provider/manager
• performing business logic

Summary

The view tells the presenter when user interaction events happen.

• The presenter can tell the view: "ok now, I can tell the interactor that I need some information from my service!".

or

• the presenter can tell to the view: "oops, the email argument you pass me is not a valid email address, so display this message: 'invalid email address'".