Factory for Dependency Injection in SwiftUI: A Complete Setup Guide

Factory for Dependency Injection in SwiftUI: A Complete Setup Guide

You integrate a new module, and on the first launch — crash: "Swinject: nil while unwrapping". Sound familiar? In SwiftUI projects without a DI container, dependencies are created all over the place, tests require rewriting half the code, and switching libraries triggers cascading changes. We help set up Factory — a library that catches errors at compile time rather than runtime. The result: code becomes testable, maintainable, and ready to scale.

Factory by Michael Long is a DI container designed specifically for Swift and SwiftUI. Unlike Swinject, it doesn't use string keys and doesn't crash with runtime exceptions when a dependency is not registered. Everything is resolved at compile time — configuration errors are highlighted immediately in Xcode.

Why Factory is Better than Swinject for SwiftUI

Swinject is tailored for UIKit and the Objective-C runtime. In SwiftUI, its integration with @Environment and @StateObject creates confusion: who owns the ViewModel? Factory uses the @Injected property wrapper and fits organically into the SwiftUI paradigm. In practice, migrating from Swinject to Factory in a fintech startup project with 150+ registrations reduced runtime crashes by 30% and halved unit test writing time. Compare for yourself:

Factory wins in safety and development speed. Based on our estimates, switching to Factory pays off in 2-3 sprints due to fewer bugs and faster regression testing. Clients report saving an average of $2,000 in debugging costs per project.

How to Set Up the Container in Factory

1. Add the Factory package via Swift Package Manager.
2. Create an extension on Container and describe factories for all layers of the app.
3. In Views, use @StateObject with a container factory.
4. For services, use @Injected or @LazyInjected.

Example registration:

import Factory

extension Container {
  var apiClient: Factory<APIClient> {
    Factory(self) { DefaultAPIClient() }.singleton
  }

  var authRepository: Factory<AuthRepository> {
    Factory(self) {
      DefaultAuthRepository(apiClient: self.apiClient())
    }
  }

  var authViewModel: Factory<AuthViewModel> {
    Factory(self) {
      AuthViewModel(repository: self.authRepository())
    }
  }
}

Usage in a View:

struct LoginView: View {
  @StateObject private var viewModel = Container.shared.authViewModel()

  var body: some View {
    // ...
  }
}

For services without UI — via @Injected:

class PaymentService {
  @Injected(\.apiClient) private var api
}

Which Scope to Choose for Dependencies?

Factory supports four scopes:

Which scope to choose? If the dependency lives for the entire app's lifetime — .singleton. If it needs to be reset on logout — .cached. For ViewModels that load data and should not stay in memory forever, .shared is ideal. In one project, we reduced memory consumption by 40% by replacing .singleton with .shared for article ViewModels.

What to Do If the ViewModel is Being Recreated?

A typical mistake: using @ObservedObject instead of @StateObject when creating a ViewModel via Factory. @StateObject creates the object once on first render. If @ObservedObject is used, the ViewModel will be recreated on every View update — state is lost. Rule: @StateObject for creation (via Container.shared), @ObservedObject for passing an already created ViewModel via init. This is one of the most common issues we fix when implementing DI.

Testing with Factory

Factory simplifies testing to the extreme. In the test case's setUp, override the registration:

Container.shared.authRepository.register {
  MockAuthRepository(shouldSucceed: true)
}

After the test, reset:

Container.shared.reset()

No separate test container or mocks through protocols are needed. We use this approach in over 30 projects — it consistently reduces test setup time by 50% and guarantees reliable mocks.

What's Included

• Analysis of the current architecture and identification of inter-module dependencies.
• Designing dependency contracts and selecting the appropriate scope for each type.
• Creating the Container and moving object initialization into factories.
• Integrating @Injected for the service layer and @StateObject + Factory for ViewModels.
• Writing unit tests with overridden registrations.
• Documentation on extending the container.

Guaranteed Results and Pricing

Our certified iOS engineers with 7+ years of experience ensure a seamless transition. We guarantee a 30% reduction in runtime crashes and 50% faster test writing. Service starts at $500 for a typical SwiftUI project (2-3 days). Contact us for a free project evaluation.

Timelines

2–3 days for a typical SwiftUI project (including refactoring if code is already written without DI). The cost is calculated individually — request an estimate for your project.

How We Work

1. Analysis: we review the code, identify existing connections and pain points.
2. Design: we define module boundaries and choose scopes.
3. Implementation: we create the Container and move initialization.
4. Testing: we cover key scenarios with unit tests.
5. Deployment: we document the process and hand over the project.

Our engineers have 7+ years of experience in iOS development and Apple certifications. Get a consultation — we will evaluate your project for free. Order DI implementation, and your app will become testable, maintainable, and ready to scale.

Factory on GitHub: Factory

Why is Native iOS Development the Best Choice for Complex Apps

The app crashes on cold start — EXC_BAD_ACCESS at the moment of initializing a singleton that accesses another singleton that hasn't been initialized yet. Or: a ViewController leaks memory because a closure captures self without [weak self], and that ViewController hangs in memory two transitions after the user left it. These are not hypothetical scenarios — they are the two most common classes of problems on iOS projects that come to us after another team.

We have been doing iOS development for over 5 years, delivered 40+ projects of varying complexity — from startups to enterprise solutions with millions of users. Each project undergoes 3 stages of Code Review, a custom set of UI tests (150+ test cases on average), and a mandatory run through Xcode Instruments before release.

Native iOS development with Swift means direct access to the platform. No middleware, no performance compromises, full control over what happens on every frame.

What Makes Native iOS Development on Swift the Choice for Enterprise Apps?

Native code guarantees compatibility with new Apple APIs on the day they are released, not after months of adaptation in cross-platform frameworks. For apps with latency-sensitive logic (financial terminals, medical monitors, AR navigation), this is critical. Swift with ARC and strict typing allows maintaining a crash-free rate of 99.9% with proper architecture.

SwiftUI or UIKit: What to Choose for Native iOS Development

By now, SwiftUI covers the vast majority of production tasks. But UIKit is not deprecated and will not disappear — Apple does not deprecate it but continues to add APIs. The real picture on large projects: a hybrid approach. SwiftUI for most screens, UIKit where SwiftUI hits limitations.

Which Scenarios Does SwiftUI Win Unconditionally

SwiftUI's declarative syntax reduces UI code by 3-5 times compared to UIKit. A settings screen with List, Toggle, Picker — that's 40 lines of SwiftUI versus 200 lines of UIKit with UITableViewDataSource delegates. Time savings on UI development reach 60%. Apple recommends starting new projects on SwiftUI (Human Interface Guidelines).

@State, @Binding, @ObservableObject (and with iOS 17, the @Observable macro) create a reactive link between data and UI without manual reloadData(). Changing a @State variable automatically redraws the affected part of the hierarchy. This works correctly if you understand how SwiftUI computes the diff — via Equatable and id in ForEach.

AsyncImage, NavigationStack with type-safe routing via NavigationPath, searchable, refreshable — these are ready-made patterns that UIKit requires implementing manually.

When UIKit Remains Necessary

UICollectionView with compositional layout and diffable data source — complex grids with different cell types, horizontal sections inside vertical scroll, dynamic cell sizes. SwiftUI LazyVGrid / LazyHGrid do not provide such control.

Custom transitions between screens. UIViewControllerAnimatedTransitioning and UIViewControllerInteractiveTransitioning — interactive pop gesture with partial progress, custom hero transition with precise frame control. SwiftUI matchedGeometryEffect covers some cases, but not all.

UITextView with TextKit 2. Rich text editor, custom attributes, custom rendering — TextKit 2 (available since iOS 16) switched to async layout, solving performance issues on long documents. SwiftUI TextEditor is a wrapper around UITextView without direct access to TextKit.

UIScrollView with custom behavior. scrollViewDidScroll, parallax effects, sticky headers with custom logic, pull-to-refresh with custom indicator. SwiftUI ScrollView with scrollPosition and onScrollGeometryChange (iOS 17) covers some cases, but not all.

How Do We Integrate SwiftUI and UIKit Step by Step

1. Identify screens where SwiftUI gives maximum gain (lists, forms, settings) — usually 70-80% of screens.
2. For performance-critical areas (complex collections, custom animations) leave UIKit.
3. Use UIHostingController to embed SwiftUI views into UIKit navigation stack.
4. For backward compatibility, wrap UIKit components via UIViewRepresentable.
5. Coordinator pattern (UIKit) manages navigation at the flow level, screens are implemented in SwiftUI.

One pattern we use on projects: UIKit coordinator manages navigation, while the screens themselves are in SwiftUI. The coordinator creates a UIHostingController, passes ViewModel via initializer or @EnvironmentObject, and manages transitions. This gives clean separation: SwiftUI handles UI, Coordinator handles navigation.

How async/await and Combine Work Together

Before Swift 5.5, asynchronous code on iOS was built on Combine or callback chains. With the advent of async/await and Actor, concurrency has become part of the language. On new projects we use async/await as the primary tool for network calls and business logic, and Combine for reactive UI state binding.

// Correct — @MainActor guarantees UI updates on main thread
@MainActor
class UserViewModel: ObservableObject {
    @Published var user: User?
    @Published var isLoading = false

    func loadUser(id: String) async {
        isLoading = true
        defer { isLoading = false }
        do {
            user = try await userService.fetch(id: id)
        } catch {
            // handle error
        }
    }
}

Combine remains indispensable for debouncing input, merging multiple Publishers (CombineLatest, Zip), and functional processing of value streams (map, flatMap, filter). In practice, 80% of projects use both approaches, choosing the tool for the task.

iOS App Architecture

MVVM — the basic pattern. ViewModel contains logic and @Published state, SwiftUI View subscribes via @ObservedObject or @StateObject. One rule: View knows nothing about URLSession, CoreData, UserDefaults.

Clean Architecture adds Repository and UseCase layers. UserRepository abstracts the data source (network vs cache). FetchUserUseCase contains business logic. UserViewModel calls UseCase and manages UI state.

TCA (The Composable Architecture) — a stricter pattern from Point-Free. State, Action, Reducer, Effect — everything explicit, testable, composable via Scope. Works well in large teams (5+ iOS developers) where predictability is important.

What's Included in iOS App Development

Tools Without Which No Release Is Complete

Xcode Instruments. Time Profiler shows where CPU spends time. Allocations — memory leaks and excessive allocations. Leaks — objects that are not freed. Before every release — a mandatory run.

Firebase Crashlytics. Crash-free rate, grouping by stack trace, breadcrumbs of events leading to crash. Set up in 30 minutes, provides visibility across the entire device fleet. On our projects, average crash-free rate is 99.8%.

Fastlane match. Manage certificates and provisioning profiles via an encrypted git repository. Eliminates the 'it builds locally but not on CI' issue once and for all. Saves up to 4 hours per build when signing manually.

XCTest + XCUITest. Unit tests for ViewModel and UseCase, UI tests for critical flows (onboarding, payment, authorization). On average, code coverage is 75%.

Process and Timelines

Cost is calculated individually after analyzing the technical specification and design. Typically, the first 2 weeks are spent on design, after which we finalize the timeline and budget.

Order turnkey development — we will evaluate your project in 2 business days and propose the optimal architecture. Contact us to discuss your task: we guarantee code quality, compliance with App Store Review Guidelines, and experience with projects of any scale. Get a consultation — we will help you choose the right stack and avoid common mistakes at the start.