@Published properties in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a property that automatically notifies views when it changes.

iOS Swift

class ViewModel: ObservableObject {
  [1] var count = 0
}

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

A@State

B@ObservedObject

C@Published

D@Binding

Attempts:

3 left

💡 Hint

Common Mistakes

Using @State instead of @Published inside ObservableObject.

Forgetting to mark the class as ObservableObject.

The @Published attribute marks a property so that changes to it notify any observing views.

2fill in blank

medium

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

iOS Swift

class ViewModel: [1] {
  @Published var name = ""
}

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

AIdentifiable

BView

CStateObject

DObservableObject

Attempts:

3 left

💡 Hint

Common Mistakes

Using View or StateObject instead of ObservableObject for the class.

Not conforming to any protocol.

ObservableObject is the protocol that allows a class to notify views about changes in @Published properties.

3fill in blank

hard

Fix the error in the code by completing the property declaration to notify views.

iOS Swift

class Settings: ObservableObject {
  [1] var isOn = false
  func toggle() {
    isOn.toggle()
  }
}

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

AAdd @Published before isOn

BAdd @State before isOn

CAdd @Binding before isOn

DAdd @ObservedObject before isOn

Attempts:

3 left

💡 Hint

Common Mistakes

Using @State or @Binding inside ObservableObject classes.

Not marking the property at all.

Only properties marked with @Published notify views when they change inside ObservableObject classes.

4fill in blank

hard

Fill both blanks to declare a published property and initialize it.

iOS Swift

class UserSettings: ObservableObject {
  [1] var username: String = [2]
}

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

A@Published

B"Guest"

C""

Dvar

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting @Published.

Initializing with empty quotes instead of a meaningful default.

The property must be marked @Published and initialized with a string value like "Guest".

5fill in blank

hard

Fill all three blanks to create a published integer property with a default value and a method to increment it.

iOS Swift

class Counter: ObservableObject {
  [1] var count: Int = [2]
  func increment() {
    count [3] 1
  }
}

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

A@Published

B0

C+=

D-=

Attempts:

3 left

💡 Hint

Common Mistakes

Using -= instead of += to increment.

Not marking count as @Published.

The count property is marked @Published, starts at 0, and increments by 1 using +=.