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A Closer Look at iOS Architecture Patterns

· 3 min read

Why Should We Care About Architecture?​

The answer is: to reduce the human resources spent on each feature.

Mobile developers evaluate the quality of an architecture on three levels:

  1. Whether the responsibilities of different features are evenly distributed
  2. Whether it is easy to test
  3. Whether it is easy to use and maintain
Responsibility DistributionTestabilityUsability
Tight Coupling MVC❌❌✅
Cocoa MVC❌ V and C are coupled❌✅⭐
MVP✅ Independent view lifecycle✅Average: more code
MVVM✅Average: View has a dependency on UIKitAverage
VIPER✅⭐️✅⭐️❌

Tight Coupling MVC​

Traditional MVC

For example, in a multi-page web application, when you click a link to navigate to another page, the entire page reloads. The problem with this architecture is that the View is tightly coupled with the Controller and Model.

Cocoa MVC​

Cocoa MVC is the architecture recommended by Apple for iOS developers. Theoretically, this architecture allows the Controller to decouple the Model from the View.

Cocoa MVC

However, in practice, Cocoa MVC encourages the use of massive view controllers, ultimately leading to the view controller handling all operations.

Realistic Cocoa MVC

Although testing such tightly coupled massive view controllers is quite difficult, Cocoa MVC performs the best in terms of development speed among the existing options.

MVP​

In MVP, the Presenter has no relationship with the lifecycle of the view controller, allowing the view to be easily replaced. We can think of UIViewController as the View.

Variant of MVC

There is another type of MVP: MVP with data binding. As shown in the figure, the View is tightly coupled with the Model and Controller.

MVP

MVVM​

MVVM is similar to MVP, but MVVM binds the View to the View Model.

MVVM

VIPER​

Unlike the three-layer structure of MV(X), VIPER has a five-layer structure (VIPER View, Interactor, Presenter, Entity, and Routing). This structure allows for good responsibility distribution but has poorer maintainability.

VIPER

Compared to MV(X), VIPER has the following differences:

  1. The logic processing of the Model is transferred to the Interactor, so Entities have no logic and are purely data storage structures.
  2. ==UI-related business logic is handled in the Presenter, while data modification functions are handled in the Interactor==.
  3. VIPER introduces a routing module, Router, to implement inter-module navigation.

iOS Architecture Patterns Revisited

· 2 min read

Why bother with architecture?​

Answer: for reducing human resources costs per feature.

Mobile developers evaluate the architecture in three dimensions.

  1. Balanced distribution of responsibilities among feature actors.
  2. Testability
  3. Ease of use and maintainability
Distribution of ResponsibilityTestabilityEase of Use
Tight-coupling MVC❌❌✅
Cocoa MVC❌ VC are coupled❌✅⭐
MVP✅ Separated View Lifecycle✅Fair: more code
MVVM✅Fair: because of View's UIKit dependantFair
VIPER✅⭐️✅⭐️❌

Tight-coupling MVC​

Traditional MVC

For example, in a multi-page web application, page completely reloaded once you press on the link to navigate somewhere else. The problem is that the View is tightly coupled with both Controller and Model.

Cocoa MVC​

Apple’s MVC, in theory, decouples View from Model via Controller.

Cocoa MVC

Apple’s MVC in reality encourages ==massive view controllers==. And the view controller ends up doing everything.

Realistic Cocoa MVC

It is hard to test coupled massive view controllers. However, Cocoa MVC is the best architectural pattern regarding the speed of the development.

MVP​

In an MVP, Presenter has nothing to do with the life cycle of the view controller, and the View can be mocked easily. We can say the UIViewController is actually the View.

MVC Variant

There is another kind of MVP: the one with data bindings. And as you can see, there is tight coupling between View and the other two.

MVP

MVVM​

It is similar to MVP but binding is between View and View Model.

MVVM

VIPER​

There are five layers (VIPER View, Interactor, Presenter, Entity, and Routing) instead of three when compared to MV(X). This distributes responsibilities well but the maintainability is bad.

VIPER

When compared to MV(X), VIPER

  1. Model logic is shifted to Interactor and Entities are left as dumb data structures.
  2. ==UI related business logic is placed into Presenter, while the data altering capabilities are placed into Interactor==.
  3. It introduces Router for the navigation responsibility.

About Tian Pan

Driven technology architect and entrepreneur with deep expertise in building highly-scalable, enterprise-grade SaaS applications. Full-stack specialist with a strong focus on designing flexible, scalable solutions that meet complex, evolving demands.

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