NVC: NanoViewController

An extremely opinionated UIKit architecture built on top of MVVM-C allowing you to create UIViewControllers declaratively with as little as a single line of code.

Show me code

A quick inline taste of the architecture — for a runnable toy example and a real-world app see Showcase.

// MARK: NanoViewController
public final class SignUpScene: Scene<SignUpView> { // 🤯 3 lines VC! 
    public static let title = "Sign Up"
}

// MARK: View
public final class SignUpView: UIView {
	private lazy var nameField: 	UITextField 			= { ... }()
	private lazy var emailField: 	UITextField 			= { ... }()
	private lazy var submitButton: 	UIButton 				= { ... }()
	private lazy var spinner: 		UIActivityIndicatorView = { ... }()
}
extension SignUpView: ViewModelled {
    public typealias ViewModel = SignUpViewModel

    public var inputFromView: InputFromView {
        InputFromView(
            name: nameField.textPublisher.orEmpty,
            email: emailField.textPublisher.orEmpty,
            submitTrigger: submitButton.tapPublisher
        )
    }

    public func populate(with output: ViewModel.Output) -> [AnyCancellable] {
        output.isSubmitEnabled 	--> submitButton.isEnabledBinder
        output.loadingText 		--> submitButton.titleBinder(for: .normal)
        output.isLoading 		--> spinner.isAnimatingBinder
    }
}

// MARK: ViewModel.InputFromView
public extension SignUpViewModel {
	struct InputFromView {
		public let name: AnyPublisher<String, Never>
		public let email: AnyPublisher<String, Never>
		public let submitTrigger: AnyPublisher<Void, Never>
	}
}

// MARK: ViewModel.Output
public extension SignUpViewModel {
	struct Output {
		public let isSubmitEnabled: AnyPublisher<Bool, Never>
		public let isLoading: AnyPublisher<Bool, Never>
	}
}

// MARK: ViewModel.InputFromView
public final class SignUpViewModel: BaseViewModel<
    SignUpUserAction, // NavigationStep
    SignUpViewModel.InputFromView,
    SignUpViewModel.Output
> {
	private let service: SignUpServicing
	/* BaseViewModel declared `public let navigator = Navigator<NavigationStep>()` */
	/* BaseViewModel declared `public var cancellables = Set<AnyCancellable>()` */

	// MARK: BaseViewModel Overrides
    override public func transform(input: Input) -> Output {
        let activity = ActivityIndicator()

        // Name + email both non-empty → form is valid.
        let isFormValid: AnyPublisher<Bool, Never> = input.fromView.name
            .combineLatest(input.fromView.email)
            .map { name, email in
                !name.trimmingCharacters(in: .whitespaces).isEmpty
                    && !email.trimmingCharacters(in: .whitespaces).isEmpty
            }
            .eraseToAnyPublisher()

        let isLoading = activity.asPublisher()

        // Submit is enabled only when the form is valid AND we're not already
        // mid-request (prevents double-taps from firing two sign-ups).
        let isSubmitEnabled = isFormValid
            .combineLatest(isLoading)
            .map { valid, loading in valid && !loading }
            .eraseToAnyPublisher()

        // On submit-tap: snapshot the latest (name, email), call the service
        // (tracking activity), forward the resulting user as `.signedUp`.
        input.fromView.submitTrigger
            .withLatestFrom(input.fromView.name.combineLatest(input.fromView.email))
            .map { [service] name, email in
                service.signUp(name: name, email: email)
                    .trackActivity(activity)
            }
            .switchToLatest()
            .sink { [weak navigator] user in
                navigator?.next(.signedUp(user))
            }
            .store(in: &cancellables)

        return Output(
            isSubmitEnabled: isSubmitEnabled,
            isLoading: isLoading
        )
    }
}

// MARK: NavigationStep
public enum SignUpUserAction: Sendable {
    case signedUp(SignedUpUser)
}

Library products

The package ships six independent SPM library targets so consumers can pick exactly what they need:

Product	Layer	Notes
NanoViewControllerCore	value types	ViewModelType, InputType, EmptyInitializable, AbstractViewModel, AbstractTarget, ActivityIndicator, ErrorTracker
NanoViewControllerCombine	reactive	Binder, the --> operator, Publisher+Extras, UIControl/UITextField/UIView publisher extensions
NanoViewControllerNavigation	coordinators	Coordinating, BaseCoordinator, Navigator, Stepper
NanoViewControllerController	UIKit glue	SceneController<View>, BarButtonContent, InputFromController, ViewModelled, NavigationBarLayoutingNavigationController, Toast
NanoViewControllerSceneViews	UIKit views	AbstractSceneView, BaseScrollableStackViewOwner, BaseTableViewOwner, SingleCellTypeTableView, CellConfigurable, pull-to-refresh / class-identifiable / footer plumbing
NanoViewControllerDIPrimitives	DI protocols	Clock, MainScheduler, DateProvider, HapticFeedback, Pasteboard, UrlOpener

Combine, Navigation, Controller, SceneViews, DIPrimitives all depend on Core. UIKit modules (Controller, SceneViews, DIPrimitives) need iOS 26+; pure value-type modules build on macOS 14+ too. Every target compiles in Swift 6.2 language mode (swift-tools-version: 6.2) so the package's @MainActor-on-UIKit annotations are enforced as hard errors at the consumer's call site.

Local development

First-time setup on a fresh clone:

brew install just     # bootstraps the rest
just bootstrap        # brew bundle install + git hooks (pre-commit + pre-push)

Then:

just test       # build + run the per-package XCTest bundles on iPhone 17 / iOS 26.1
just cov        # tests with coverage report
just fmt        # swiftformat + swiftlint --fix
just            # list every recipe

CI runs the same pipeline on every push / PR — typos check, swiftformat lint, swiftlint strict, build + test on the iOS Simulator. See .github/workflows/ci.yml.

The pre-commit hook installed by just bootstrap enforces: typos, shellcheck, swiftformat lint, swiftlint strict on every commit; and the full test suite on every push.

Showcase

SignUpDemo (toy, in this repo)

Examples/SignUpDemo/ is a small UIKit iOS app that walks through every load-bearing piece of the package: a SceneController-backed sign-up screen, a Coordinator swap on success, and a logout button on the home screen that re-runs the onboarding flow. It uses a stub SignUpServicing (instant-success) so it runs out of the box on the simulator.

just example-gen     # generate Examples/SignUpDemo/SignUpDemo.xcodeproj from project.yml
just example-build   # xcodebuild for iPhone 17 simulator
open Examples/SignUpDemo/SignUpDemo.xcodeproj   # then ⌘R in Xcode

The example shows the canonical wiring: scene = SceneController<View>, view-model subclasses the package's BaseViewModel<NavigationStep, InputFromView, Output> (which fixes FromController to InputFromController and provides a Navigator<Step>), coordinator subscribes to that navigator and routes the user-actions to push / pop / present transitions.

Zhip (real-world iOS wallet)

Zhip is a full-featured iOS wallet app built on the same architecture (originally with the predecessor "SLC: SingleLineController" — see History below). A larger, real-world example of NanoViewController in production use.

History

Implementation happened in 2018 in https://github.com/sajjon/zhip (originally https://github.com/openzesame/zhip); then called "SLC: SingleLineController". You can read my blog posts from 2018, part one and part two - since ported from RxSwift to Combine and extracted into this separate repo.