Binding

struct · iOS 13.0+ · SDK 27.1

@frozen @propertyWrapper @dynamicMemberLookup struct Binding<Value>

A property wrapper type that can read and write a value owned by a source of truth. Use a binding to create a two-way connection between a property that stores data, and a view that displays and changes the data. A binding connects a property to a source of truth stored elsewhere, instead of storing data directly. For example, a button that toggles between play and pause can create a binding to a property of its parent view using the `Binding` property wrapper. struct PlayButton: View { @Binding var isPlaying: Bool var body: some View { Button(isPlaying ? "Pause" : "Play") { isPlaying.toggle() } } } The parent view declares a property to hold the playing state, using the ``State`` property wrapper to indicate that this property is the value's source of truth. struct PlayerView: View { var episode: Episode @State private var isPlaying: Bool = false var body: some View { VStack { Text(episode.title) .foregroundStyle(isPlaying ? .primary : .secondary) PlayButton(isPlaying: $isPlaying) // Pass a binding. } } } When `PlayerView` initializes `PlayButton`, it passes a binding of its state property into the button's binding property. Applying the `$` prefix to a property wrapped value returns its ``State/projectedValue``, which for a state property wrapper returns a binding to the value. Whenever the user taps the `PlayButton`, the `PlayerView` updates its `isPlaying` state. A binding conforms to ``Sendable`` only if its wrapped value type also conforms to ``Sendable``. It is always safe to pass a sendable binding between different concurrency domains. However, reading from or writing to a binding's wrapped value from a different concurrency domain may or may not be safe, depending on how the binding was created. SwiftUI will issue a warning at runtime if it detects a binding being used in a way that may compromise data safety. > Note: To create bindings to properties of a type that conforms to the <doc://com.apple.documentation/documentation/Observation/Observable> protocol, use the ``Bindable`` property wrapper. For more information, see <doc:Migrating-from-the-observable-object-protocol-to-the-observable-macro>.

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