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.