mobiai-ios-architecture

iOS Architecture

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Common architecture patterns in iOS apps.

When to Use

• Navigating an unfamiliar iOS codebase
• Understanding where to make changes
• Writing code that follows existing patterns

Detecting the Architecture

# Check for SwiftUI vs UIKit
grep -r "import SwiftUI" --include="*.swift" -l | wc -l
grep -r "import UIKit" --include="*.swift" -l | wc -l

# Check for architecture indicators
grep -r "ViewModel\|UseCase\|Repository\|Interactor\|Presenter\|Store\|Reducer" --include="*.swift" -l | head -20

# Check for Combine usage
grep -r "import Combine\|@Published\|AnyPublisher" --include="*.swift" -l | wc -l

# Check for TCA (The Composable Architecture)
grep -r "import ComposableArchitecture\|ReducerOf\|Store<" --include="*.swift" -l | head -10

MVVM + SwiftUI (Most Common Modern Pattern)

Structure

Feature/
  Views/
    MyView.swift              # SwiftUI View
    MyDetailView.swift
  ViewModels/
    MyViewModel.swift         # ObservableObject with @Published
  Models/
    MyModel.swift             # Data models
  Services/
    MyService.swift           # API/data access

Patterns

// ViewModel
@MainActor
class MyViewModel: ObservableObject {
    @Published var items: [Item] = []
    @Published var isLoading = false
    @Published var error: Error?

    private let repository: ItemRepository

    init(repository: ItemRepository) {
        self.repository = repository
    }

    func loadItems() async {
        isLoading = true
        defer { isLoading = false }
        do {
            items = try await repository.fetchItems()
        } catch {
            self.error = error
        }
    }
}

// View
struct MyView: View {
    @StateObject private var viewModel = MyViewModel(repository: .live)

    var body: some View {
        List(viewModel.items) { item in
            Text(item.name)
        }
        .task { await viewModel.loadItems() }
    }
}