Pooja Prajapati
Written By Pooja Prajapati Sr. iOS Developer

Viper Architecture in iOS Development: A Comprehensive Guide

post date
February 2, 2024
Viper Architecture in iOS Development A Comprehensive Guide
Reading Time: 9 minutes

In the domain of software development, the idea that “we sculpt our code, and subsequently, our code sculpts us” remains valid. Just as architects thoughtfully plan and organize buildings, programmers must shape their code with clarity and purpose. This concept is embodied in the term “software architecture,” where each component is easily identifiable, serves a distinct purpose, and smoothly integrates with other elements.

While effective software architecture doesn’t guarantee a product’s success, it is pivotal in ensuring the product’s maintainability and preserving the sanity of the developers involved.

In this exploration, we delve into an iOS application architecture known as VIPER. Acclaimed for its application in large-scale projects, VIPER provides a systematic approach to software design. To exemplify its principles, we undertake the task of constructing a to-do list app, deciphering the intricacies of VIPER as we navigate through the development process.

What is the VIPER Architecture?

VIPER stands for View, Interactor, Presenter, Entity, and Router. It’s a software design pattern for building modular and testable applications, often used in mobile development, particularly for iOS apps.

Think of it as a layered approach to organizing your code, where each layer has a specific responsibility and interacts with other layers through well-defined interfaces. This separation of concerns makes the code easier to understand, maintain, and test.

Viper Architecture


The View serves as the UI conduit, bridging the gap between user gestures and app responses. It captures touches, scrolls, and clicks, translating them into commands it relays to the Presenter. In return, the Presenter provides data and instructions, which the View then uses to update the interface, keeping users informed and engaged.

Code of View:

import UIKit
class LiveNewsListViewController: UIViewController {
    @IBOutlet weak var tblview: UITableView!
    var presenter: LiveNewsListViewToPresenterProtocol?
    var newsData = [LiveNewsModel]()
    override func viewDidLoad() {
        LiveNewsRouter.createModule(viewRef: self)
        tblview.rowHeight = 200
    func setUpTableView() {
        self.tblview.dataSource = self
        self.tblview.delegate = self
        let nib = UINib(nibName: "LiveNewsTableViewCell", bundle: nil)
        tblview.register(nib, forCellReuseIdentifier: "LiveNewsTableViewCell")
extension LiveNewsListViewController: UITableViewDelegate, UITableViewDataSource {
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return newsData.count
 func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "LiveNewsTableViewCell", for: indexPath) as? LiveNewsTableViewCell
        let newsData = newsData[indexPath.row]
        cell?.lblTitle.text = "Title: \(newsData.title ?? "")"
        cell?.lblAuthor.text = "Author: \(newsData.author ?? "")"
        cell?.lblDescription.text = "Description: \(newsData.description ?? "")"
        return cell!
extension LiveNewsListViewController: LiveNewsListPresenterToViewProtocol {
    func showNews(news: [LiveNewsModel]) {
        self.newsData = news
    func showError() {
        let alert = UIAlertController(title: "Alert", message: "Problem Fetching News", preferredStyle: UIAlertController.Style.alert)
        alert.addAction(UIAlertAction(title: "Okay", style: UIAlertAction.Style.default, handler: nil))
        self.present(alert, animated: true, completion: nil)


The Interactor serves as the data engine, handling all processing and retrieval tasks. It interacts with APIs like a seasoned diplomat, negotiates data access, manipulates the information according to business rules, and then hands it off to the Presenter for consumption and presentation.

Code Of Interactor:

import Foundation
import Alamofire
class LiveNewsInteractor: LiveNewsListPresenterToInteractorProtocol {
    // MARK: - Properties
    weak var presenter: LiveNewsListInteractorToPresenterProtocol?
    var news: [LiveNewsModel]?
    // MARK: - Methods
    func fetchLiveNews() {
        AF.request(<YourAPI>).response { response in
            If (response.response?.statusCode == 200) {
                guard let data = response.data else { return }
                do {
                    let decoder = JSONDecoder()
                    let newsResponse = try decoder.decode(NewsResponse.self, from: data)
                    guard let article = newsResponse.articles else { return }
                    self.news = article
                    self.presenter?.liveNewsFetched(news: self.news ?? [])
                } catch let error {
            else {


The Presenter acts as the data alchemist, transforming raw inputs from the View into polished presentations. It orchestrates communication with the Interactor, extracting and manipulating data according to defined rules. Finally, it crafts a beautiful visual narrative for the View to display, ensuring user engagement and understanding.

Code of Presenter:

import Foundation
class LiveNewsPresenter: LiveNewsListViewToPresenterProtocol {
    // MARK: - Properties
    weak var view: LiveNewsListPresenterToViewProtocol?
    var interactor: LiveNewsListPresenterToInteractorProtocol?
    var router: LiveNewsListPresenterToRouterProtocol?
    // MARK: - Methods
    func updateView() { 
// MARK: - LiveNewsListInteractorToPresenterProtocol
extension LiveNewsPresenter: LiveNewsListInteractorToPresenterProtocol {
    func liveNewsFetched(news: [LiveNewsModel]) {
        view?.showNews(news: news)
    func liveNewsFetchedFailed() {


The Entity represents the data models used in the application. It defines the structure of the data and is responsible for encapsulating the data-related properties and methods

Code of Entity:

import Foundation

struct NewsResponse: Codable {
    let status: String?
    let source: String?
    let sortBy: String?
    let articles: [LiveNewsModel]?

struct LiveNewsModel: Codable {
    let author: String?
    let title: String?
    let description: String?
    let url: String?
    let urlToImage: String?
    let publishedAt: String?


The Router handles navigation between different modules and manages the transitions between screens. It ensures that the navigation logic is separate from other components.

Code of Router:

import Foundation
import UIKit
class LiveNewsRouter: LiveNewsListPresenterToRouterProtocol {
    // MARK: - Methods
    class func createModule(viewRef: LiveNewsListViewController) {
        let presenter: LiveNewsListViewToPresenterProtocol & LiveNewsListInteractorToPresenterProtocol = LiveNewsPresenter()
        viewRef.presenter = presenter
        viewRef.presenter?.view = viewRef
        viewRef.presenter?.router = LiveNewsRouter()
        viewRef.presenter?.interactor = LiveNewsInteractor()
        viewRef.presenter?.interactor?.presenter = presenter

VIPER Architecture with Protocols

Viper is a delegation-driven architecture. So, most of the communication between different layers is executed through delegation. One layer calls another through a protocol. The calling layer calls a function from a protocol. The listening layer conforms to that protocol and implements the function.

Viper adheres to a strict naming convention for protocols, like “viewToPresenterProtocol.” These act as blueprints, defining the messages the presenter listens for from the view, ensuring clear and structured communication.

  • PresenterToViewProtocol: The communication bridge, defines the messages the presenter sends to the view. The presenter holds a reference to this protocol, allowing it to “speak” to the view, which in turn, faithfully implements the protocol’s instructions.
  • ViewToPresenterProtocol: View calls, Presenter listens.
  • InteractorToPresenterProtocol: Interactor calls, Presenter listens.
  • PresenterToInteractorProtocol: Presenter calls, Interactor listens.
  • PresenterToRouterProtocol: Presenter calls, Router listens.

Code of Protocol:

import Foundation
import UIKit
protocol LiveNewsListPresenterToViewProtocol: AnyObject {
    func showNews(news: [LiveNewsModel])
    func showError()
protocol LiveNewsListInteractorToPresenterProtocol: AnyObject {
    func liveNewsFetched(news: [LiveNewsModel])
    func liveNewsFetchedFailed()
protocol LiveNewsListPresenterToInteractorProtocol: AnyObject {
    var presenter: LiveNewsListInteractorToPresenterProtocol? { get set }
    var news: [LiveNewsModel]? { get }
    func fetchLiveNews()
protocol LiveNewsListViewToPresenterProtocol: AnyObject {
    var view: LiveNewsListPresenterToViewProtocol? { get set }
    var interactor: LiveNewsListPresenterToInteractorProtocol? { get set }    var router: LiveNewsListPresenterToRouterProtocol? { get set }
    func updateView()
protocol LiveNewsListPresenterToRouterProtocol: AnyObject {
    static func createModule(viewRef: LiveNewsListViewController)

Also, protocol names must be different for different modules. One way to achieve this is to add the module name as a prefix. So the format could be e.g if the module name is Login then view to presenter protocol name will be LoginViewToPresenterProtocol.

Advantages of VIPER Architecture

The VIPER architecture, standing for View, Interactor, Presenter, Entity, and Router, offers numerous advantages for building robust and maintainable mobile applications. These advantages fall into four key categories:

1. Enhanced Modularity and Maintainability:

  • Organized codebase: VIPER separates functionality into distinct layers, each with a clear responsibility. Imagine a well-labelled kitchen – utensils in drawers, ingredients on shelves. This makes the code easier to understand, navigate, and maintain.
  • Simplified updates and bug fixes: Targeting specific layers isolates changes and minimizes ripple effects, reducing maintenance time and complexity.
  • Faster onboarding for new developers: The clear structure and defined roles in VIPER allow new developers to quickly grasp the codebase and contribute effectively.

2. Boosted Testability:

  • Targeted unit testing: Each layer can be tested independently, focusing on its specific functionality. This makes testing more efficient and pinpoints bugs with greater precision.
  • Improved code quality: Thoroughly tested layers lead to robust and reliable code, minimizing crashes and performance issues for users.
  • Automated testing support: VIPER’s clear boundaries simplify the implementation of automated test frameworks, further enhancing code quality and stability.

3. Increased Scalability and Collaboration:

  • Parallel development: Teams can work on different layers simultaneously, accelerating development for complex projects. Imagine separate teams preparing ingredients, cooking dishes, and setting the table – all progressing independently yet contributing to the same meal.
  • Easier feature integration: Adding new features becomes a matter of plugging in additional modules, preserving the architecture’s integrity and scalability.
  • Reduced code conflicts: Defined roles and clear communication protocols between layers minimize merge conflicts and maintain code consistency.

4. Clear Separation of Concerns:

  • Focused layers: Each layer handles a specific task, preventing logic leaks and tangled dependencies. This leads to cleaner, more maintainable code.
  • Reusability potential: Frequently used functionalities within layers can be packaged as independent modules, promoting code reuse across the app or even in future projects.
  • Enhanced developer understanding: The separation of concerns clarifies responsibilities and makes the codebase easier to understand for individual developers and teams.

The VIPER architecture empowers developers to build robust, maintainable, and scalable mobile applications with improved testability and efficient collaboration. By fostering a well-organized and focused codebase, VIPER sets the stage for a smoother development process and a superior user experience.

Disadvantages of VIPER

While VIPER offers numerous advantages, it’s not without its downsides. Here’s a rundown of the potential drawbacks you might encounter:

1. Increased Complexity:

  • Steeper learning curve: Compared to simpler architectures, VIPER’s layered structure and distinct roles can be more challenging to grasp for beginners. Imagine building a complex Lego set compared to a basic one – more pieces, more instructions, more potential for confusion.
  • Initial setup overhead: Setting up the various layers and protocols in VIPER can be time-consuming, especially for small projects where the benefits may not outweigh the initial effort.
  • Potentially larger codebase: The separation of concerns can lead to more files and classes, which can feel cumbersome for some developers. Think of a sprawling kitchen pantry compared to a minimalist one – more organization, but also potentially more clutter.

2. Overkill for Simple Projects:

  • Unnecessary complexity: For small projects with limited functionality, VIPER’s structure might be overkill, adding unnecessary complexity and overhead. Imagine using a powerful blender for a simple smoothie – overkill for the task at hand.
  • Potentially slower development: The initial setup and modularity can initially slow down development compared to simpler architectures. Think of building a house with pre-fab modules versus traditional brick-and-mortar construction – faster with modules, but less flexibility.

3. Potential Performance Overhead:

  • Increased layer communication: Data flowing between layers can introduce a slight performance overhead compared to architectures with less separation. Imagine a game of telephone with many people – the message might get muddled or delayed.
  • Over-abstraction pitfalls: Overly complex abstractions within layers can lead to performance bottlenecks and difficulty optimizing the code. Think of using a heavy filter on a photo – it can enhance certain aspects, but also obscure details or slow down processing.

4. Team Communication Challenges:

  • Clear understanding is crucial: Everyone on the development team needs to understand the VIPER structure and protocols to avoid communication issues and inconsistencies. Think of a band where everyone plays their own tune – it won’t sound good without coordinated communication.
  • Potential integration hurdles: Integrating third-party libraries or frameworks can be challenging due to potential conflicts with VIPER’s structure and protocols. Imagine trying to fit a square peg in a round hole – it might require adjustments or workarounds.

Ultimately, the decision to use VIPER depends on the specific needs and context of your project. Weigh the potential benefits and drawbacks carefully to determine if it’s the right fit for your development journey.

When to Consider the VIPER Design Pattern

The VIPER architecture, characterized by distinct layers and clear separation of concerns, can be a powerful tool for developing robust and maintainable mobile applications. However, its advantages come with a slight learning curve and increased complexity. So, when should you consider wielding the VIPER approach? Here are some scenarios where it excels:

1. Complex and Scalable Projects:

  • Feature-rich Applications: Imagine building a multifaceted e-commerce app with numerous screens, functionalities, and integrations. VIPER’s modularity and scalability will keep things organized and manageable as the app grows.
  • Long-term Development Roadmap: If your app is envisioned for long-term growth and continuous updates, VIPER’s structure provides a stable foundation for adding new features without compromising existing code.
  • Large Development Teams: With multiple developers working on different parts of the app, VIPER’s clear roles and communication protocols facilitate efficient collaboration and avoid code conflicts.

2. Prioritizing Testability and Maintainability:

  • Robust Codebase: VIPER’s layered structure allows for unit testing of each component in isolation, leading to a more bug-free and reliable app. Imagine a meticulously maintained machine – each component is easily checked and serviced, ensuring smooth operation.
  • Simplified Bug Hunting: With clear boundaries between layers, pinpointing and fixing bugs becomes a more targeted and efficient process. Imagine troubleshooting a complex system – isolating the faulty component makes repairs quicker and easier.
  • Future-proof Codebase: The separation of concerns and focus on reusable modules in VIPER make it easier to maintain and adapt the codebase to changing requirements and technologies over time. Think of a modular building – adding new floors or wings is much easier compared to a monolithic structure.

3. Collaboration and Code Clarity:

  • Defined Roles and Responsibilities: Each layer in VIPER has a clear purpose, making it easier for developers to understand their tasks and collaborate effectively. Imagine a well-rehearsed orchestra – each instrument knows its part, contributing to the overall harmony.
  • Reduced Knowledge Silos: The separation of concerns prevents developers from needing deep knowledge of the entire codebase, making it easier for new team members to contribute. Think of a well-organized library – you can find the information you need without needing to know everything on every shelf.
  • Improved Code Comprehension: The modularity and clear interfaces in VIPER make the codebase easier to understand and navigate, even for developers unfamiliar with the project. Think of a well-written recipe – anyone can follow the instructions and achieve successful results.

However, before diving headfirst into VIPER, consider these scenarios where it might not be the ideal choice:

  • Small and Simple Apps: For basic apps with limited functionality, the overhead of setting up and using VIPER might outweigh the benefits. Imagine using a high-tech tool for a simple task – simpler options might be quicker and more efficient.
  • Tight Deadlines and Limited Resources: If you’re pressed for time or have a small team, the initial learning curve and setup overhead of VIPER might not be feasible. Think of building a Lego set with a looming deadline – simpler alternatives might be faster to complete.
  • Unfamiliar Development Team: If your team is not familiar with design patterns like VIPER, the learning curve and potential communication challenges might hinder productivity. Imagine teaching a new language – it takes time and patience to become fluent.

Ultimately, the decision to use VIPER should be based on a careful assessment of your project’s needs, resources, and team expertise. Weigh the potential benefits and drawbacks to determine if VIPER will be the architect of your development success.


In this comprehensive guide, we’ve explored the intricacies and potential of the VIPER architecture, showcasing how its layered structure, clear separation of concerns, and focused modules empower iOS developers to craft robust, maintainable, and scalable applications.

While VIPER offers a powerful toolset, choosing the right approach for your project is crucial. For complex, feature-rich apps with long-term visions and large development teams prioritizing testability and code clarity, VIPER can be the architect of your success. However, for simpler apps with tight deadlines or unfamiliar teams, alternative approaches might be more efficient.

Regardless of your decision, building a successful iOS application takes expertise and collaboration. This is where our iOS Development company comes in. We boast a team of experienced iOS developers, and experts in various architectures and frameworks, including VIPER, ready to assist in your projects. Whether you need guidance on choosing the right approach, tackling complex architectural challenges, or simply adding extra firepower to your development team, WebCodeGenie is here to partner with you.

Pooja Prajapati
Written By Pooja Prajapati Sr. iOS Developer

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