iOS Architectural Patterns: The Beginner Guide

iOS architectural patterns refer to the different ways in which iOS developers organize and structure the codebase of their apps. When it comes to developing iOS apps, it’s important to choose the right architectural pattern in the beginning or at least adapt one as soon as possible. Choosing the right pattern can help you build an application that is scalable, maintainable, and reusable. On the other hand, choosing the wrong pattern can lead to a codebase that is difficult to maintain and debug. In this article, we’ll explore some of the most commonly used iOS architectural patterns and discuss their benefits, drawbacks, and how to use them effectively.

What is Architecture Pattern?

Architecture patterns refer to the patterns that are used to structure and organize the code in an iOS application. It’s like the blueprint that defines how different parts of the code will interact with each other and how the app will be built. Now, let’s take the example of a house. Just like a house has a structure and a layout, an iOS app also needs to have a structure to make it functional and user-friendly. And just like a house can be built using different architectural styles, an iOS app can also be built using different architecture patterns.

For example, let’s say you’re building a weather app. The view would be responsible for displaying the temperature, the model would contain the data for the current weather conditions, and the controller would handle the user input and communicate with the model to update the view accordingly.

Another popular architecture pattern is the Model-View-ViewModel (MVVM) pattern. This pattern is similar to MVC, but the view is more loosely coupled from the model. In this pattern, the view interacts directly with the ViewModel, which handles the data and business logic, and the ViewModel communicates with the model to update the view. Using the same weather app example, the ViewModel would handle the logic for displaying the temperature, the view would be responsible for displaying the data, and the model would provide the data for the ViewModel to use.

What is The Most Common Objective of Architecture Patterns?

Architecture Pattern! Every iOS developer has their favorite one. The widely-used MVC pattern is ubiquitous, while the MVVM pattern is the talk of the town, preferred by the iOS community. VIPER and Clean swift, on the other hand, are considered complicated, but they offer an unparalleled level of flexibility.

Although these architectural patterns may have different names, they are all based on the same objective – to separate concerns. They all achieve this by segmenting the application into layers, each with its own unique function and responsibility. When it comes to selecting an architecture for your next mind-boggling iOS app, there are many aspects to consider. But one thing is certain: by embracing the separation of concerns and segmenting your app into layers, you will create an app that is inherently testable, resulting in all the advantages that come with it.

How Can Architecture Patterns Aid Teams in Handling Complexity During iOS App Development?

iOS architecture patterns are essential for iOS app development teams because they provide a clear structure and organization for the code, making it easier to develop, maintain, and scale the app. Here are some reasons why iOS architecture patterns are necessary.

1. Separation of Concerns: Architecture patterns separate the different concerns of an app, such as the user interface, data, and business logic. This separation makes it easier to manage the complexity of the app and makes it easier for different team members to work on different parts of the code.
2. Code Reusability: A well-architected app allows for greater code reusability, which saves time and effort in development. By separating concerns, teams can create components that can be reused throughout the app and even in other projects.
3. Testability: Architecture patterns make it easier to test the app because it’s easier to isolate and test individual components of the app. This makes it easier to catch bugs and issues early in development and makes the app more reliable.
4. Maintainability: A well-architected app is easier to maintain and update because changes can be made to specific components without affecting other parts of the app. This reduces the risk of introducing bugs and makes it easier to add new features and improve the app over time.
5. Scalability: Architecture patterns make it easier to scale the app as the project grows. By separating concerns and creating reusable components, teams can add new features and functionality without having to rewrite large portions of the code.

What is the Best/Optimal Architectural Pattern?

It’s important to understand that each architecture pattern has its own strengths and weaknesses, and the “best” pattern really depends on the specific needs and requirements of the app being developed. So, it’s really not fair to compare one architectural pattern to another and say that one is better than the other Instead, we should focus on understanding the key principles and concepts behind each architecture pattern and use that knowledge to choose the most appropriate pattern for the specific project.

One more thing is that each architecture pattern has a unique set of best practices and coding standards that need to be followed to ensure that the codebase is well-structured and maintainable. This means that instead of debating which architecture pattern is the best, we should focus on learning and applying the best practices associated with each pattern.

Why Should Architecture Patterns Be Part of the Learning Journey for Junior iOS Developers?

I believe that learning about iOS architecture patterns is definitely a good idea because they are widely used in the iOS development industry, and knowing about them can make us a valuable developer. It shows that you will be familiar with industry-standard practices and can help you stand out in a competitive job market. However, Some patterns can be complex and may take time to fully understand, and it can be difficult to apply them in practice. Additionally, it can be difficult to know which pattern to use for a specific project.

Common iOS Architectural Patterns

Model-View-Controller (MVC) pattern

The Model-View-Controller pattern is the most widely used pattern in iOS development. This pattern separates the UI into the Model that represents the application state, the View, which is composed of UI controls, and a Controller which handles user interactions and updates the model accordingly.

But, let’s be honest here – the MVC pattern isn’t without its challenges. One big problem is that it can be quite confusing to implement. Despite the seemingly clear-cut relationships between the Model, View, and Controller, in practice it’s easy to end up with a tangled web of code that becomes a big, horrible mess.

In this pattern,

• The model: This component is responsible for data management and business logic.
• The view: This component is responsible for presenting data to the user and handling user interactions.
• The controller: This component acts as an intermediary between the model and the view. It’s responsible for coordinating the flow of data between the two components.

One of the key benefits of the MVC pattern is that it’s easy to understand and implement. However, the drawback of this pattern is that it can lead to a bloated view controller, which makes it difficult to maintain and test.

Model-View-ViewModel (MVVM) pattern

Let’s talk about the MVVM pattern – a powerful architecture pattern that has gained popularity in recent years, thanks in part to Apple’s release of Combine and SwiftUI. The heart of MVVM is ViewModel – a special type of model that represents the UI state of the app. It’s like the conductor of an orchestra, coordinating all the different UI controls and ensuring that they work together seamlessly. The ViewModel contains properties that detail the state of each and every UI control, like the current text for a text field or whether a specific button is enabled. It also exposes the actions that the view can perform, like button taps or gestures. And with the release of Combine, MVVM becomes an even more natural choice. Combine provides logical streams of data that can emit values over time, making it easy to cleanly define a chain that starts in your UI and ends with a network call.

But what sets MVVM apart from other patterns like MVC is its strict rules for component relationships. For example, the view has a reference to the ViewModel, but not vice versa. The ViewModel has a reference to the Model, but not vice versa. If you break any of these rules, you’re doing MVVM wrong.

One immediate advantage of this pattern is that all your UI logic resides within the ViewModel, resulting in a very lightweight view. This makes it much easier to manage and test your code. In fact, you can run your entire app without the View, greatly enhancing its testability. However, the drawback of this pattern is that it can be difficult to implement, especially if you’re new to iOS development. So if you’re looking to build a powerful, flexible iOS app, the MVVM pattern is definitely worth exploring. With its clear rules and emphasis on testability, it’s a solid choice for any project.

Model-View-Presenter (MVP) pattern

The Model-View-Presenter pattern is also similar to the MVC pattern, but it replaces the controller with a presenter. The presenter is responsible for coordinating the flow of data between the view and the model. It’s also responsible for updating the view when the model changes.

The benefit of the MVP pattern is that it separates the view logic from the business logic, which makes it easier to test and maintain. However, the drawback of this pattern is that it can lead to a bloated presenter, which makes it difficult to maintain.

MVVM-C

MVVM-C stands for Model-View-ViewModel-Coordinator, which is an architectural pattern used in Swift and other programming languages for developing iOS apps.

The MVVM-C pattern builds on top of the traditional MVVM pattern by adding a coordinator layer. The coordinator is responsible for managing the navigation flow between different views or screens in the app, as well as handling other complex application-level tasks.

In the MVVM-C pattern, the model represents the data of the app and the business logic. The view displays the data and reacts to user inputs. The view model acts as an intermediary between the view and the model, providing the data and transforming it as needed for display purposes.

The coordinator, on the other hand, manages the navigation between different views or screens in the app, and handles any other application-level tasks that require coordination between multiple view controllers.

VIPER

VIPER is an architectural pattern that builds upon the foundation laid by MVC and MVVM. However, unlike these patterns, VIPER takes the idea of single responsibility even further. The problem with the Apple-style MVC is that it encourages developers to cram all the app logic into a UIViewController subclass. VIPER, like its predecessor MVVM, seeks to solve this issue by separating the code into different components, each with a specific responsibility.

In VIPER, the user interface is represented by the View. The Interactor acts as a mediator between the Presenter and the data, taking instructions from the Presenter. The Presenter directs the data flow between the View and the Interactor, handling user actions and calling upon the Router to move the user between different views. The Entity, on the other hand, represents the application data that needs to be processed. The Router is responsible for handling the navigation between different screens within the app. With VIPER, each component has its own unique responsibility, allowing for easier maintenance and testing of the codebase.

• View is responsible for the user interface.
• Interactor acts as a mediator between the Presenter and the data layer, taking instructions from the Presenter to fetch or manipulate data.
• Presenter manages the flow of data between the View and the Interactor, responding to user actions and calling on the Router to navigate between screens.
• Entity represents the application’s data, typically encapsulating it in a data model or business object.
• Router is responsible for managing the navigation between screens, providing a clean separation of concerns for the app’s navigation logic.

Clean Swift / VIP

The Clean Architecture pattern is designed to make the codebase of an application more modular and testable. The architecture consists of multiple layers, each with its own responsibilities and dependencies. In the Clean Swift methodology, your code is organized around each application screen or segment of screens, which are referred to as “scenes”. Each scene is designed to have a well-defined structure that consists of six distinct components:

• View Controller
• Interactor
• Presenter
• Worker
• Models
• Router

The three primary components of Clean Swift are the view controller, interactor, and presenter. The view controller’s output is linked to the interactor’s input, which in turn feeds into the presenter’s input. The presenter then processes the data and sends it back to the view controller. This creates a unidirectional flow of control that simplifies the code and makes it easier to maintain.

With this structure in place, each scene becomes a self-contained module that can be easily reused and tested. By separating the concerns of each component, the code becomes more modular, which allows for faster development and better overall design.

Uber’s RIB Framework

RIBs is an architecture framework that underpins many mobile apps at Uber, providing a solid foundation for large-scale projects with nested states. Its name comes from its core components: Router, Interactor, and Builder.

This architecture offers several benefits, including cross-platform compatibility between iOS and Android, making it easier for teams to collaborate and review business logic code. It also prioritizes testability and isolation, with RIB classes having distinct responsibilities that are easy to unit test and reason about independently. What sets RIBs apart from other architecture patterns, such as MVC, MVP, VIP, MVVM, and VIPER, is its business logic-driven approach. Unlike other patterns, RIBs does not require views and instead prioritizes independent business logic and view trees. This allows for a deep business logic tree that is isolated from view hierarchies, making it easy to maintain a shallow view hierarchy that is simple to layout, animate, and transition.

A good illustration from ByteByteGo:

Last words,

When it comes to choosing an architectural pattern for an iOS app, it’s important to consider a few key factors. You’ll want to choose an architecture that aligns with the app’s specific requirements, including its complexity, size, and feature set. You’ll also want to consider factors like the team’s experience and the app’s potential for future growth and scalability. Choosing the right architectural pattern for your iOS app can have a significant impact on its maintainability, scalability, and overall success of your app. By carefully evaluating your options and considering all relevant factors, you can make an informed decision that meets the needs of both your team and your users.

Thanks for reading!

✍️ Written by Ishtiak Ahmed

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