iOS
SwiftUI Composable Architecture: Building Modular and Scalable Apps
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Problem Statement
Managing the state of large apps becomes challenging as the codebase grows. Without a structured architecture, it’s difficult to isolate business logic for testing and code reuse.
Solution
We adopted the Composable Architecture (TCA) to modularize our app’s logic. This approach enabled clear separation of state, view and side effects, promoting scalability, reusability and testability.
What is Compositional Architecture?
Composable Architecture is a predictable state management library for SwiftUI apps. Its popularity gained from the open source framework called "The Composable Architecture" or TCA by Point Free. A composable architecture follows three principles:
- State Management: The centralized, immutable application state.
- Side Effects: Controlled and predictable through dependency.
- Composability: The decomposition of an application into smaller, reusable parts.
TCA provides a set of tools and patterns that enable one to structure the app and then you focus on features rather than being burdened with ever increasing complexity.
Why is it useful to do Composable Architecture?
1. Predictable state management
Ensures that any app's state is consistent as well as predictable, thus debuggable and in reason about their code.
2. Testability
TCA separates state, action, and a side effect easily, so when it comes to unit testing each component, every component can thus be tested standalone, ensuring high reliability.
3. Scalability
This problem is further multiplied as the applications grow. Here, TCA's composable and modular structure helps scale an app by encapsulating features, eliminating duplicate code.
4. Code Reusability
Common logic may be abstracted and reused within other parts of an app with the help of TCA, reducing development time while improving maintainability.
How to Implement Composable Architecture
Let’s dive into implementing a simple example using TCA. We’ll build a counter app with the ability to increment, decrement and reset the counter.
1. Defining the State
State is the struct that describes the data of a given feature
struct CounterState: Equatable {var count: Int = 0}
2. Defining the Actions
Actions enumerate the user interactions and events for a feature.
struct CounterState: Equatable {
var count: Int = 0
}
3. Creating the Reducer
A reducer describes how actions modify the state and defines side effects.
import ComposableArchitecture
let counterReducer = Reducer<CounterState, CounterAction, Void> { state, action, _ in
switch action {
case .increment:
state.count += 1
return .none
case .decrement:
state.count -= 1
return .none
case .reset:
state.count = 0
return .none
}
}
4. Building the View
The view binds to the state and dispatches actions through a Store.
import ComposableArchitecture
let counterReducer = Reducer<CounterState, CounterAction, Void> { state, action, _ in
switch action {
case .increment:
state.count += 1
return .none
case .decrement:
state.count -= 1
return .none
case .reset:
state.count = 0
return .none
}
}
5. Integrating in the App
@main
struct MyApp: App {
var body: some Scene {
WindowGroup {
CounterView(
store: Store(
initialState: CounterState(),
reducer: counterReducer,
environment: ()
)
)
}
}
}What are Benefits of Composable Architecture
1. Better Modularization: Features are independent and may be developed in parallel.
2. Higher Quality Code: Separation of concerns makes the code cleaner and easier to maintain.
3. It makes debugging easy as its state and action flow is deterministic.
4. Reusability: The same pattern and logic are reused across the application.
5. Comprehensive Testing: Parts are tested in isolation
Key Takeaways
- Composable architecture is extremely powerful for designing modular, scalable and testable SwiftUI applications.
- Separation of Concerns: Grouping state, actions and reducers together ensures a clean separation of concerns.
* While it presents a learning curve, the eventual payoff that will come is worth every effort in long run benefits hence is ideal for large and complicated applications.
Therefore, with TCA the quality of the app is improved in the development process hence, try it out in your next SwiftUI project!
Where to use composable architecture?
1. Multifunctional Applications: Applications with multiple features and interdependent states benefit the most from TCA.
2. Enterprise Solutions: Long term projects that are maintainable and scalable.
3. Collaborative Development: Teams developing large apps with modular architecture
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