How to use ViewBuilder in SwiftUI

Issue #877 Over the course of making several SwiftUI apps, I鈥檝e discovered quite a few hidden magic of SwiftUI that are quite fun. Here are 6 interesting SwiftUI features in View Builder many don鈥檛 know are even possible 馃く View protocol with enum Struct is not the only way to describe #SwiftUI views. Learn how you can achieve the same thing with just enum Conform primitive type to View protocol You can also conform any value type or primitive type to View protocol...

April 11, 2022 路 2 min 路 Khoa Pham

How to debounce TextField search in SwiftUI

Issue #876 Make a dedicate DebounceObject to debounce (or throttle). Then we can even observe with onChange on the debouncedText or just use it directly to sort public final class DebounceObject: ObservableObject { @Published var text: String = "" @Published var debouncedText: String = "" private var bag = Set<AnyCancellable>() public init(dueTime: TimeInterval = 0.5) { $text .removeDuplicates() .debounce(for: .seconds(dueTime), scheduler: DispatchQueue.main) .sink(receiveValue: { [weak self] value in self?.debouncedText = value }) ....

March 26, 2022 路 1 min 路 Khoa Pham

How to pop multiple level with NavigationView and NavigationLink in SwiftUI

Issue #858 Use isActive and isDetailLink(false) Use Introspect .introspectNavigationController { nav in self.nav = nav } Read more

January 27, 2022 路 1 min 路 Khoa Pham

How to show QR code in SwiftUI

Issue #855 Use CoreImage to generate QR image import SwiftUI import CoreImage.CIFilterBuiltins struct QRView: View { let qrCode: String @State private var image: UIImage? var body: some View { ZStack { if let image = image { Image(uiImage: image) .resizable() .interpolation(.none) .frame(width: 210, height: 210) } } .onAppear { generateImage() } } private func generateImage() { guard image == nil else { return } let context = CIContext() let filter = CIFilter....

January 15, 2022 路 1 min 路 Khoa Pham

How to disable with ButtonStyle in SwiftUI

Issue #853 With ButtonStyle, the disabled modifier does not seem to work, we need to use allowsHitTesting. import SwiftUI struct ActionButtonStyle: ButtonStyle { func makeBody(configuration: Configuration) -> some View { HStack { Text("Button") } .padding() .disabled(true) // does not work .allowsHitTesting(false) } } We need to call disabled outside, after buttonStyle. In case we have onTapGesture on the entire view, touching on that disabled button will also trigger our whole view action, which is not what we want....

December 4, 2021 路 1 min 路 Khoa Pham

How to use dynamic shape in SwiftUI

Issue #850 Erase with AnyShape struct AnyShape: Shape { init<S: Shape>(_ wrapped: S) { innerPath = { rect in let path = wrapped.path(in: rect) return path } } func path(in rect: CGRect) -> Path { return innerPath(rect) } private let innerPath: (CGRect) -> Path } extension Shape { func erase() -> AnyShape { AnyShape(self) } } Then we can use like private struct ContentView: View { var body: some View { ZStack { Color....

September 30, 2021 路 1 min 路 Khoa Pham

How to use Picker with optional selection in SwiftUI

Issue #849 We need to explicitly specify optional in tag extension AVCaptureDevice: Identifiable { public var id: String { uniqueID } } @State var device: AVCaptureDevice? Picker("Camera", selection: $device) { ForEach(manager.devices) { d in Text(d.localizedName) .tag(AVCaptureDevice?.some(d)) } }

September 30, 2021 路 1 min 路 Khoa Pham

How to scale system font size to support Dynamic Type

Issue #847 We should use Dynamic Font Type as much as possible, as per Typography guide and But in case we have to use a specific font, we can scale it with UIFontMetrics import SwiftUI import UIKit extension Font { static func system( scaledSize size: CGFloat, weight: Font.Weight = .regular, design: Font.Design = .default ) -> Font { Font.system( size: UIFontMetrics.default.scaledValue(for: size), weight: weight, design: design ) } } Then instead of...

September 2, 2021 路 1 min 路 Khoa Pham

How to round specific corner in SwiftUI

Issue #846 We use UIBezierPath with addArc to draw specific corner with different rounding values. import SwiftUI extension View { func clipCorners( topLeft: CGFloat = 0, bottomLeft: CGFloat = 0, topRight: CGFloat = 0, bottomRight: CGFloat = 0 ) -> some View { clipShape( SpecificCornerShape( topLeft: topLeft, bottomLeft: bottomLeft, topRight: topRight, bottomRight: bottomRight ) ) } } struct SpecificCornerShape: Shape { var topLeft: CGFloat = 0 var bottomLeft: CGFloat = 0 var topRight: CGFloat = 0 var bottomRight: CGFloat = 0 func path(in rect: CGRect) -> Path { let minX = rect....

August 26, 2021 路 2 min 路 Khoa Pham

How to show suffix text in TextField in SwiftUI

Issue #845 Suppose we have struct Payment as the state, we declare custom Binding<String> that derives from our state. struct Payment { var amount: Int = 0 } To show our suffix view, we use .fixedSize(horizontal: true, vertical: false) to constrain our TextField to fit content, and to avoid it to grow outside our frame, we constrain a max limit, like 10_000 in this case. An interesting thing is we divide by 10 to not let the newly typed digit enter if the amount is above our limit...

August 24, 2021 路 1 min 路 Khoa Pham

How to show currency symbol in TextField in SwiftUI

Issue #844 Use custom Binding and validate the text. In case of zero, return empty string to let TextField display placeholder var textField: some View { let text = Binding<String>( get: { state.amount > 0 ? "$\(state.amount)" : "" }, set: { text in let text = text.replacingOccurrences(of: "$", with: "") state.amount = Int(text) ?? 0 } ) return TextField("$0", text: text) .keyboardType(.numberPad) .font(.system(size: 50, weight: .medium, design: .monospaced)) .foregroundColor(Asset.textPrimary.color) ....

August 24, 2021 路 1 min 路 Khoa Pham

How to make multiline message text view in SwiftUI

Issue #843 This can be used in message bar input or some popover form. We use sizeThatFits to calculate the height so that it grow under certain height limit import SwiftUI import UIKit struct MessageTextField: View { let placeholder: String @Binding var text: String @Binding var isEditing: Bool @State private var height: CGFloat = 100 var body: some View { UITextViewWrapper( text: $text, isEditing: $isEditing, height: $height ) .frame(height: height) ....

August 21, 2021 路 2 min 路 Khoa Pham

How to read safe area insets in SwiftUI

Issue #842 Declare EnvironmentKey and read safeAreaInsets from key window in connectedScenes struct SafeAreaInsetsKey: EnvironmentKey { static var defaultValue: EdgeInsets { UIApplication.shared.keyWindow?.safeAreaInsets.swiftUIInsets ?? EdgeInsets() } } private extension UIEdgeInsets { var swiftUIInsets: EdgeInsets { EdgeInsets(top: top, leading: left, bottom: bottom, trailing: right) } } private extension UIApplication { var keyWindow: UIWindow? { connectedScenes .compactMap { $0 as? UIWindowScene } .flatMap { $ } .first { $0.isKeyWindow } } } struct MessageBar: View { @Environment(\....

August 20, 2021 路 1 min 路 Khoa Pham

How to make tab strip with enum cases in SwiftUI

Issue #841 Declare generic on RawRepresentable import SwiftUI struct TabStrip<T: RawRepresentable & Hashable>: View where T.RawValue == String { let values: [T] @Binding var selected: T var body: some View { ScrollView(.horizontal, showsIndicators: false) { LazyHStack(spacing: 24) { ForEach(values, id: \.self) { value in Button(action: { selected = value }) { Text(value.rawValue) .foregroundColor(selected == value ? Asset.textPrimary.color : Asset.textSecondary.color) .fontWeight(selected == value ? .semibold : .regular) .padding(6) } .buttonStyle(PlainButtonStyle()) } } } ....

August 19, 2021 路 1 min 路 Khoa Pham

How to map Binding with optional value in SwiftUI

Issue #838 We can write our custom Binding import SwiftUI extension Binding where Value == Date? { func flatten(defaultValue: Date) -> Binding<Date> { Binding<Date>( get: { wrappedValue ?? defaultValue }, set: { wrappedValue = $0 } ) } } Then use in places where it needs Binding with non-optional value DatePicker( "", selection: $date.flatten(defaultValue: Date()), displayedComponents: .hourAndMinute ) .datePickerStyle(WheelDatePickerStyle())

August 10, 2021 路 1 min 路 Khoa Pham

How to get view height in SwiftUI

Issue #837 I usually use GeometryReader in background to get size of view, and encapsulate it inside a ViewModifier struct GetHeightModifier: ViewModifier { @Binding var height: CGFloat func body(content: Content) -> some View { content.background( GeometryReader { geo -> Color in DispatchQueue.main.async { height = geo.size.height } return Color.clear } ) } } This is useful to constrain NavigationView height when in use inside a bottom sheet struct FilterView: View { @State private var height: CGFloat = 0 var body: some View { BottomSheet { NavigationView { VStack { Text("content") } ....

August 6, 2021 路 1 min 路 Khoa Pham

How to prevent wheel Picker conflict with DragGesture in SwiftUI

Issue #836 If we have a Picker inside a View that has DragGesture, chances are when we scroll the wheel, the DragGesture is detected too To prevent this, we can attach a dummy DragGesture to our Picker Picker("", selection: $number) { ForEach(FavoriteNumbers.allCases) { number in Text( } } .pickerStyle(WheelPickerStyle()) .gesture(DragGesture())

August 5, 2021 路 1 min 路 Khoa Pham

How to make equal width buttons in SwiftUI

Issue #835 I usually define ButtonStyle to encapsulate common styles related to buttons. Here we specify .frame(maxWidth: .infinity) to let this button take the whole width as possible struct MyActionButtonStyle: ButtonStyle { func makeBody(configuration: Configuration) -> some View { configuration.label .font(.headline.bold()) .foregroundColor(.white) .frame(height: 44) .frame(maxWidth: .infinity) .background( .cornerRadius(8) } } If we have 2 buttons both specifying maxWidth: .infinity then they will be divided equally with a spacing specified by our HStack...

August 5, 2021 路 1 min 路 Khoa Pham

How to make bottom sheet in SwiftUI

Issue #834 In iOS 15, we can use UISheetPresentationController to show bottom sheet like native Maps app. But before that there鈥檚 no such built in bottom sheet in UIKit or SwiftUI. We can start defining API for it. There are 3 ways to show overlay content in SwiftUI fullScreenCover: this presents like a modal view controller bottom up offset: initially hide our bottom sheet overlay: show overlay full screen so we can have custom control....

August 5, 2021 路 2 min 路 Khoa Pham

How to bind to nested ObservableObject in SwiftUI

Issue #831 We can normally listen to sub ObservableObject by either listen to its objectWillChange or its Publisher class SubModel: ObservableObject { @Published var count = 0 } class AppModel: ObservableObject { @Published var submodel: SubModel = SubModel() private var bag = Set<AnyCancellable>() init() { submodel.$count .sink(receiveValue: { [weak self] _ in self?.objectWillChange.send() }) } } We can then make a convenient extension to ease this. We use DispatchQueue to trigger objectWillChange in another run loop, to achieve didSet behavior...

July 27, 2021 路 1 min 路 Khoa Pham