UIViewKit lets you build UIKit views directly in code with a syntax that feels like SwiftUI. It provides a DSL powered by @resultBuilder for both UIView hierarchies and NSLayoutConstraints, so you can create entire UIViewController scenes in strongly typed Swift - without relying on storyboards or XIBs.
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DSL with @resultBuilder for UIKit - Build UIView hierarchies in Swift using a declarative, SwiftUI-like syntax. With builders like ibSubviews, ibAttributes, and ibApply, your code becomes compact, expressive, and easy to read.
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Constraint Generator - Define AutoLayout with ibConstraints for fast, expressive, and compact constraint definitions.
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FreeForm Preview - Instantly preview UIKit views and controllers with live constraint evaluation. Test layouts across multiple device sizes without leaving Xcode.
import UIViewKit class ViewController: UIViewController { override func viewDidLoad() { super.viewDidLoad() view.ibSubviews { UILabel().ibAttributes { $0.centerXAnchor.constraint(equalTo: view.centerXAnchor) $0.centerYAnchor.constraint(equalTo: view.centerYAnchor) $0.text = "Hello, world!" } } } }final class ViewController: UIViewController { private var profileItems: [(title: String, value: String)] = [ ("Framework: ", "UIViewKit"), ("Platform: ", "iOS"), ("Programming Language: ", "Swift"), ("Device:" , "Simulator"), ("FreeForm Preview:" , "UIKit, SwiftUI"), ] private var headerView: UIStackView! override func loadView() { super.loadView() view.ibSubviews { UIStackView(axis: .vertical, alignment: .fill).ibOutlet(&headerView).ibSubviews { UIImageView().ibAttributes { $0.widthAnchor.constraint(equalTo: $0.heightAnchor).ibPriority(.required) $0.image = .init(systemName: "person.circle") $0.contentMode = .scaleAspectFit $0.tintColor = .white $0.layer.cornerRadius = 20 $0.backgroundColor = .systemBlue } }.ibAttributes { $0.leadingAnchor.constraint(equalTo: view.leadingAnchor) $0.topAnchor.constraint(equalTo: view.topAnchor) $0.trailingAnchor.constraint(equalTo: view.trailingAnchor) $0.backgroundColor = .systemGreen $0.layoutMargins = .init(top: 20, left: 20, bottom: 20, right: 20) $0.isLayoutMarginsRelativeArrangement = true } UIStackView(axis: .vertical).ibSubviews { for item in profileItems { RowView().ibAttributes { $0.titleLabel.text = item.title $0.valueLabel.text = item.value } } UIView() }.ibAttributes { $0.topAnchor.constraint(equalTo: headerView.bottomAnchor) $0.leadingAnchor.constraint(equalTo: view.leadingAnchor) $0.trailingAnchor.constraint(equalTo: view.trailingAnchor) $0.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor) } }.ibAttributes { $0.backgroundColor = .systemBackground } } } final class RowView: UIView { var titleLabel: UILabel! var valueLabel: UILabel! required init?(coder: NSCoder) { fatalError() } override init(frame: CGRect) { super.init(frame: frame) self.ibSubviews { UIStackView(axis: .vertical).ibSubviews { UIStackView(axis: .horizontal, spacing: 10).ibSubviews { UILabel().ibOutlet(&titleLabel) UILabel().ibOutlet(&valueLabel).ibAttributes { $0.textColor = .systemGray $0.textAlignment = .right } } UIView().ibAttributes { $0.heightAnchor.constraint(equalToConstant: 1) $0.backgroundColor = .separator } }.ibAttributes { $0.leadingAnchor.constraint(equalTo: layoutMarginsGuide.leadingAnchor) $0.topAnchor.constraint(equalTo: topAnchor) $0.trailingAnchor.constraint(equalTo: layoutMarginsGuide.trailingAnchor) $0.bottomAnchor.constraint(equalTo: bottomAnchor) $0.heightAnchor.constraint(equalToConstant: 66) } } } }import SwiftUI #Preview { IBFreeForm { ViewController() } }
- ibSubviews - Define the hierarchy of views, similar to Interface Builder's Document Outline. When applied to a UIStackView, the DSL uses the
addArrangedSubviewmethod - ibAttributes - Configure attributes and constraints of a view. This corresponds to Interface Builder’s Identity, Attributes, Size, and Connections Inspectors.
- ibApply - Similar to ibAttributes, but without a @resultBuilder for constraints — useful for custom configurations, it works with NSObject and UIView
- IBFreeForm - Wraps a UIView, UIViewController, or even a SwiftUI.View, allowing resizing in the simulator. You can also define a snapFrame to display frames of specific devices (e.g., iPhone SE).
- IBDebug - Provides showColors, showFrames to help visualize layout frames during debugging. Works only with UIKit.