Thinking about code – the origins of TCA

Created by Brandon Williams and Stephen Celis, The Composable Architecture was born out of a desire to address some of the common issues and complexities associated with building robust and maintainable iOS applications.

TCA leverages functional programming concepts and Swift's type system to offer a modern and elegant solution for iOS app architecture. Another way of thinking about TCA is as a tool complementary to SwiftUI and Combine, or rather an extension of the two. Although TCA is mainly used with SwiftUI by the authors, it can be used with UIKit and other UI libraries used on any Apple platform (iOS, macOS, tvOS, and watchOS).

The Composable Architecture consists of a few key components:

1. State – a collection of all the data required to describe your app's state at a specific point in time.
2. Actions – an enumeration used to describe the possible user interactions or events that can occur in your application.
3. Reducers – functions that take the current state and an action as input and return a new state; they encapsulate the logic for transitioning from one state to another based on the action.
4. Store – a place that brings together the state, actions, and reducer; it manages the state and orchestrates the flow of actions, ensuring that the state is always updated in a consistent and predictable manner.

At its core, TCA encourages developers to think about their code in a more functional and declarative manner. Instead of relying on traditional imperative patterns, like in UIKit, TCA embraces functional programming principles. This shift in thinking encourages cleaner, more testable, and much easier-to-maintain code.

Strengths of The Composable Architecture

One of the main advantages of TCA is that it enforces a strict unidirectional data flow, making it easy to understand how changes in state occur in response to actions. This predictability simplifies debugging and helps prevent unexpected side effects. However, introducing this framework can provide many more benefits. What are some of the more important ones?

• Modularity: TCA encourages breaking down your application into smaller, composable components. Each feature or screen can have its own state, actions, and reducers, leading to a modular and maintainable codebase.
• SwiftUI Integration: as mentioned earlier, The Composable Architecture seamlessly integrates with SwiftUI, allowing you to build your user interfaces using a declarative and reactive approach. This combination results in a more natural and efficient way to develop iOS apps.
• Scalability: this framework scales well with the complexity of your application. As your app grows, you can continue to add new features and screens, each with its own state and logic, without sacrificing maintainability.

In addition to all of the above, The Composable Architecture has a growing community of developers and resources, including tutorials, documentation, and libraries, which makes it easier to adopt and leverage in your projects.

…But there are drawbacks too

While The Composable Architecture Framework offers numerous advantages, it's essential to be aware of potential challenges linked to its employment.

Firstly, there is the issue of the learning curve. Yes, that’s right. While declarative frameworks are indeed oriented towards ease of use and the best development experience, transitioning from traditional imperative patterns to a functional and declarative approach can be challenging for developers who are not familiar with these concepts or are simply used to imperative frameworks. It may take time to adapt to the new mindset.

Secondly, it might be too complex for basic apps. Contrary to SwiftUI, which favors simpler designs, TCA shines in complicated applications with many states and interactions. For simple projects, it might introduce unnecessary overhead and complexity.

Keeping the declarative development sorted for iOS

The Composable Architecture framework represents a paradigm shift in iOS app development. It encourages developers to think in a more functional and declarative way, resulting in cleaner, more maintainable, and testable code. By embracing immutable state, strict unidirectional data flow, and modularization, TCA offers a compelling solution for building iOS applications of any scale.

While there may be a learning curve and considerations for simpler projects, the benefits of using TCA make it a valuable addition to the toolkit of iOS developers looking to enhance their code quality and development experience.