Introduction

MVP is an architectural pattern, a derivation of the Model–View–Controller. It’s represented by three distinct components: Model, View and the Presenter. It was engineered to facilitate automated unit testing and improve the separation of concerns in presentation logic.

In examples you’ll find a simple project built with MVP pattern in mind.

Remarks

Components:

• Model is an interface responsible for the domain data (to be displayed or otherwise acted upon in the GUI)
• View is responsible for the presentation layer (GUI)
• Presenter is the “middle-man” between Model and View. It reacts to the user’s actions performed on the View, retrieves data from the Model, and formats it for display in the View

Component duties:

| Model | View | Presenter | | —— | —— | —— | | Communicates with DB layer | Renders data | Performs queries to the Model | | Raising appropriate events | Receives events | Formats data from Model | | | Very basic validation logic | Sends formatted data to the View | | | |Complex validation logic| |||

Differences between MVC and MVP:

• View in MVC is tightly coupled with the Controller, the View part of the MVP consists of both UIViews and UIViewController
• MVP View is as dumb as possible and contains almost no logic (like in MVVM), MVC View has some business logic and can query the Model
• MVP View handles user gestures and delegates interaction to the Presenter, in MVC the Controller handles gestures and commands Model
• MVP pattern highly supports Unit Testing, MVC has limited support
• MVC Controller has lots of UIKit dependencies, MVP Presenter has none

Pros:

• MVP makes UIViewController a part of the View component it’s dumb, passive and…less massive ;]
• Most of the business logic is incapsulated due to the dumb Views, this gives an excellent testability. Mock objects can be introduced to test the domain part.
• Separated entities are easier to keep in head, responsibilities are clearly divided.

Cons

• You will write more code.
• Barrier for unexperienced developers or for those who don’t yet work with the pattern.

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