Unpacking Redux and MVVM - A comparative look at the 2 architectures in Swift

I've set a goal to dig deeper into Redux, a pattern I've recently come across. My focus will be to understand its role in app architecture and state management. This exploration is part of my preparation for an upcoming personal project where I will consider using this new knowledge.

For the uninitiated, Redux is a popular JavaScript library for managing application state, but it's also found a home in Swift development. While I was diving into Redux, I realized it would be a great idea to compare it with another well-known architectural pattern - Model-View-ViewModel or MVVM, that I am more comfortable with..?Now, MVVM is a hit in the Swift community, especially with the introduction of SwiftUI and the Combine framework.

The purpose of this article, then, is to share my newfound insights about Redux and MVVM in Swift, comparing the two side by side, and discussing their pros and cons. My aim is to provide a guide that'll help you, like it helped me to make an informed choice about pattern for an app.?

Whether you're just dipping your toes into Swift, or you're a seasoned pro looking for a refresher, read on. Let's delve into Redux and MVVM in Swift!

Buckle up!

Redux in Swift

It sticks to three main principles:

1. State: Everything about your app is in one single struct or class.
2. Action: Stuff that happes?in your app. This could be a user clicking a button or a system event. These actions change the state.
3. Reducer: This is a pure function that takes in the current state and an action, and spits out a new state.

Why Redux Rocks

1. State Interactions: If your app has a lot of state to handle and many parts interacting with this state, Redux could be your friend. It gives you a single source of truth, making it easier to manage and track state changes.
2. Predictability and Debugging: Redux is like that strict teacher in school. It follows a strict set of rules for state updates, making it easy to predict and debug. Plus, when you debug it's letting you move forwards and backwards through state changes.
3. Scalability: If you're building a big app where different teams work on different features, Redux can help by enforcing a specific structure and data flow, making it easier to manage data across the application.
4. Asynchronous Actions: Redux can also help manage complex asynchronous operations, providing a more readable way to deal with these tasks.
5. Testability: Redux makes writing tests easier, thanks to its structure and strict data flow. Since state changes are predictable and based only on dispatched actions, unit tests can validate your app's logic.

Redux Downsides

Despite these cool things, Redux does add (too much?) complexity to your codebase, so it might be overkill for simpler apps. Plus, if your app's state doesn't change much or doesn't need to be shared across many components, Redux may not be the best fit.

MVVM in Swift

MVVM is a crowd favorite in the Swift community. With SwiftUI and the Combine framework, it's become even more popular. Here's what it looks like:

1. Model: This represents your app's data and business logic.
2. View: This handles the UI and user input.
3. ViewModel: This is the middleman that transforms the Model's data into values that the View/UIViewController can display.

Why MVVM is Great

1. Data Binding: If your project supports data binding (eg. with Combine), MVVM can be a natural fit. The ViewModel exposes data streams that the View binds to, simplifying the code needed to update the View.
2. Testability: MVVM boosts the testability of your code. It lets you write unit tests for your ViewModel that cover your business logic without needing to mess with the UI.
3. Complex User Interfaces: If your app has complex user interfaces with lots of dynamic content, MVVM can help manage this complexity.?
4. Code Reusability and Separation of Concerns: MVVM encourages reusable and modular code. It also keeps responsibilities separate, so developers can focus on the UI in the View without worrying about data processing, and vice versa for the ViewModel.
5. Large Teams or Projects: For big projects or teams, MVVM offers a clean structure that separates responsibilities well. This can make your codebase easier to navigate, and different parts can be worked on simultaneously, reducing the risk of merge conflicts.

MVVM's Downsides

While MVVM has some solid strengths, it's not all sunshine and roses:

1. Huge ViewModels: MVVM can sometimes create large ViewModels that can become a bit too unruly, difficult to manage and maintain.?
2. Simple Applications: If your app is just a simple one-page screen, or there's no complicated dance between your UI and business logic, using MVVM might feel like using a hammer to crack a nut.?

Some code would be nice

How Redux could look like

// Stat
struct AppState {
????var counter: Int = 0
}

// Actions
enum AppAction {
????case increment
????case decrement
}

// Reducer
func appReducer(state: inout AppState, action: AppAction) {
????switch action {
????case .increment:
????????state.counter += 1
????case .decrement:
????????state.counter -= 1
????}
}

// Usage
struct ContentView: View {
????@State private var state = AppState()

????var body: some View {
????????VStack {
????????????Text("Counter: \(state.counter)")
????????????Button("Increment") {
????????????????appReducer(state: &state, action: .increment)
????????????}
????????}
????}
}        

How MVVM could look like

// Model
struct Counter {
? ? var value: Int = 0
}

// ViewModel
class CounterViewModel: ObservableObject {
? ? @Published var counter: Counter = Counter()

? ? func increment() {
? ? ? ? counter.value += 1
? ? }

? ? func decrement() {
? ? ? ? counter.value -= 1
? ? }
}

struct ContentView: View {
? ? @ObservedObject var viewModel: CounterViewModel

? ? ? ? var body: some View {
? ? ? ? ? ? VStack {
? ? ? ? ? ? ? ? Text("Counter: \(viewModel.counter.value)")
? ? ? ? ? ? ? ? Button("Increment", action: viewModel.increment)
? ? ? ? ? ? ? ? Button("Decrement", action: viewModel.decrement)
? ? ? ? ? ? }
? ? ? ? }
}
        

The Final Face-off

So, Redux and MVVM - which one should you go with? Well, it depends on what your app needs, your personal coding style, and your project's specific requirements.

Redux is a state management champ. It brings predictability and ease of debugging to the table, but it can also bring a lot of complexity if your app is a simple one. On the other hand, MVVM plays nice with Combine, offering a clear separation of concerns that helps with code maintenance and testability. But, beware of those oversized ViewModels.

Remember, architecture choices are like clothes. What works for one person might not work for another. It's all about understanding what your project needs and picking the architecture that fits those needs like a glove. There's no one-size-fits-all answer here - every project is unique, and so should be its architecture.?

Happy coding!