SwiftUI SwiftUI State and Data Flow

Question 1

What property wrapper is used to declare local mutable state in a SwiftUI view?

Accepted Answer

@State

Answer

`@State` declares a source of truth owned by the view for simple value types.

Question 2

What does `@Binding` do in SwiftUI?

Accepted Answer

Creates a two-way connection to a state owned by another view

Answer

`@Binding` provides a reference to state stored elsewhere, allowing a child view to read and write it.

Question 3

Which property wrapper connects a view to an external ObservableObject instance?

Accepted Answer

@ObservedObject

Answer

`@ObservedObject` tells the view to re-render when the observed object's published properties change.

Question 4

What protocol must a class conform to in order to be used with `@ObservedObject` or `@StateObject`?

Accepted Answer

ObservableObject

Answer

A class must conform to `ObservableObject` and mark properties with `@Published` to trigger view updates.

Question 5

When should you use `@StateObject` instead of `@ObservedObject`?

Accepted Answer

When the view owns and creates the object

Answer

`@StateObject` should be used when the view is responsible for creating and owning the object's lifetime.

SwiftUI Practice Test