ObservedObject

struct · iOS 13.0+ · SDK 27.1

@MainActor @propertyWrapper @preconcurrency @frozen struct ObservedObject<ObjectType> where ObjectType : ObservableObject

A property wrapper type that subscribes to an observable object and invalidates a view whenever the observable object changes. Add the `@ObservedObject` attribute to a parameter of a SwiftUI ``View`` when the input is an <doc://com.apple.documentation/documentation/Combine/ObservableObject> and you want the view to update when the object's published properties change. You typically do this to pass a ``StateObject`` into a subview. The following example defines a data model as an observable object, instantiates the model in a view as a state object, and then passes the instance to a subview as an observed object: class DataModel: ObservableObject { @Published var name = "Some Name" @Published var isEnabled = false } struct MyView: View { @StateObject private var model = DataModel() var body: some View { Text(model.name) MySubView(model: model) } } struct MySubView: View { @ObservedObject var model: DataModel var body: some View { Toggle("Enabled", isOn: $model.isEnabled) } } When any published property of the observable object changes, SwiftUI updates any view that depends on the object. Subviews can also make updates to the model properties, like the ``Toggle`` in the above example, that propagate to other observers throughout the view hierarchy. Don't specify a default or initial value for the observed object. Use the attribute only for a property that acts as an input for a view, as in the above example. > Note: Don't wrap objects conforming to the <doc://com.apple.documentation/documentation/Observation/Observable> protocol with `@ObservedObject`. SwiftUI automatically tracks dependencies to `Observable` objects used within body and updates dependent views when their data changes. Attempting to wrap an `Observable` object with `@ObservedObject` may cause a compiler error, because it requires that its wrapped object to conform to the <doc://com.apple.documentation/documentation/Combine/ObservableObject> protocol. > > If the view needs a binding to a property of an `Observable` object in its body, wrap the object with the ``Bindable`` property wrapper instead; for example, `@Bindable var model: DataModel`. For more information, see <doc:Managing-model-data-in-your-app>.

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