ObservableObject protocol in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to make the class notify views about changes.

iOS Swift

class UserSettings: [1] {
  @Published var score = 0
}

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AObservableObject

BView

CState

DApp

Attempts:

3 left

💡 Hint

Common Mistakes

Using View or State instead of ObservableObject.

Forgetting to conform to any protocol.

The class must conform to ObservableObject to notify views when data changes.

2fill in blank

medium

Complete the code to mark a property that triggers view updates.

iOS Swift

class Settings: ObservableObject {
  [1] var isDarkMode = false
}

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A@State

B@EnvironmentObject

C@ObservedObject

D@Published

Attempts:

3 left

💡 Hint

Common Mistakes

Using @State inside ObservableObject class.

Using @ObservedObject or @EnvironmentObject incorrectly.

@Published marks properties that send change notifications to views.

3fill in blank

hard

Fix the error in the view to observe the object correctly.

iOS Swift

struct ContentView: View {
  [1] var settings = Settings()

  var body: some View {
    Text(settings.isDarkMode ? "Dark" : "Light")
  }
}

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A@EnvironmentObject

B@Published

C@StateObject

D@ObservedObject

Attempts:

3 left

💡 Hint

Common Mistakes

Using @ObservedObject when the view creates the object.

Using @Published in a view property.

@StateObject creates and owns the ObservableObject in the view lifecycle.

4fill in blank

hard

Fill both blanks to observe an existing object passed from parent view.

iOS Swift

struct DetailView: View {
  [1] var settings: Settings

  var body: some View {
    Toggle("Dark Mode", isOn: $settings.[2])
  }
}

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A@ObservedObject

BisDarkMode

C@StateObject

Dscore

Attempts:

3 left

💡 Hint

Common Mistakes

Using @StateObject for passed-in objects.

Binding to a property not marked @Published.

Use @ObservedObject to observe an object passed in, and bind to its @Published property.

5fill in blank

hard

Fill all three blanks to create and observe an object in a parent view and pass it to a child view.

iOS Swift

struct ParentView: View {
  [1] var settings = Settings()

  var body: some View {
    ChildView([2]: settings)
  }
}

struct ChildView: View {
  [3] var settings: Settings

  var body: some View {
    Text(settings.isDarkMode ? "Dark" : "Light")
  }
}

Drag options to blanks, or click blank then click option'

A@StateObject

Bsettings

C@ObservedObject

D@Published

Attempts:

3 left

💡 Hint

Common Mistakes

Using @ObservedObject in parent view for object creation.

Not passing the object with the correct parameter name.

Using @Published in views.

Parent uses @StateObject to create the object, passes it as 'settings', child uses @ObservedObject to observe it.