CRUD operations with SwiftData in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new SwiftData model instance and save it.

iOS Swift

let newItem = Item(name: "Sample")
context.insert(newItem)
try context.[1]()

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

Asave

Bpersist

Ccommit

Dstore

Attempts:

3 left

💡 Hint

Common Mistakes

Using methods like commit or persist which are not part of SwiftData context.

Forgetting to call save() after creating a new item.

In SwiftData, you call save() on the context to save changes like new items.

2fill in blank

medium

Complete the code to fetch all items from SwiftData context.

iOS Swift

let request = FetchDescriptor<Item>()
let items = try context.[1](request)

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

AgetAll

BfetchAll

Cretrieve

Dfetch

Attempts:

3 left

💡 Hint

Common Mistakes

Using fetchAll which is not a SwiftData method.

Using getAll or retrieve which are not valid context methods.

The fetch(_) method is used to get data matching a fetch descriptor in SwiftData.

3fill in blank

hard

Fix the error in the code to update an existing item and save changes.

iOS Swift

item.name = "Updated"
try context.[1]()

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

Asave

Bcommit

Cupdate

Dapply

Attempts:

3 left

💡 Hint

Common Mistakes

Using commit or update which are not SwiftData context methods.

Forgetting to call save() after modifying the item.

To save updates in SwiftData, you call save() on the context after changing properties.

4fill in blank

hard

Fill both blanks to delete an item from SwiftData and save the change.

iOS Swift

context.[1](item)
try context.[2]()

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

Adelete

Bremove

Csave

Dcommit

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove instead of delete which is not a SwiftData method.

Using commit instead of save to persist changes.

Use delete(_) to remove an item, then save() to persist the deletion.

5fill in blank

hard

Fill all three blanks to create a filtered fetch request for items with name longer than 5 characters.

iOS Swift

let request = FetchDescriptor<Item>(
  predicate: #Predicate { \.name.[1] [2] [3] }
)

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

Acount

B>

C5

Dlength

Attempts:

3 left

💡 Hint

Common Mistakes

Using length instead of count which is not a Swift property.

Using wrong comparison operators or values.

Use count on the string property, then compare with > and the number 5 to filter items.

Practice

1. What does the @Model attribute in SwiftData represent?

easy

A. A UI component for displaying lists

B. A data model class used to define entities for CRUD operations

C. A function to fetch data from the network

D. A SwiftUI view modifier for styling

Solution

1. Step 1: Understand the role of @Model

   The @Model attribute marks a class as a data model entity for SwiftData, enabling CRUD operations.

2. Step 2: Differentiate from UI and functions

   It is not related to UI components, network functions, or view modifiers.

3. Final Answer:

   A data model class used to define entities for CRUD operations -> Option B

4. Quick Check:

   @Model defines data entities = B [OK]

Hint: Remember @Model marks data classes, not UI or functions [OK]

Common Mistakes:

• Confusing @Model with UI components
• Thinking @Model fetches data
• Mixing @Model with view modifiers

2. Which of the following is the correct way to declare a SwiftData model class named Book with a title property of type String?

easy

A. @Model class Book { var title: String }

B. @Model struct Book { var title: String }

C. struct Book { var title: String }

D. class Book: ObservableObject { var title: String }

Solution

1. Step 1: Identify correct @Model usage

   SwiftData requires @Model on a class, not a struct, to define a data entity.

2. Step 2: Check class vs struct and attribute

   @Model class Book { var title: String } correctly uses @Model with a class and a property.

3. Final Answer:

   @Model class Book { var title: String } -> Option A

4. Quick Check:

   @Model + class + properties = D [OK]

Hint: Use @Model with class, not struct, for SwiftData models [OK]

Common Mistakes:

• Using struct instead of class for @Model
• Omitting @Model attribute
• Using ObservableObject instead of @Model

3. Given the following SwiftData code snippet, what will be the output when printing books.count after adding a new book?

struct ContentView: View {
  @Environment(\"modelContext\") private var modelContext
  @Query var books: [Book]

  var body: some View {
    Button(\"Add Book\") {
      let newBook = Book(title: \"SwiftData Basics\")
      modelContext.insert(newBook)
    }
    Text(\"Books count: \(books.count)\")
  }
}

medium

A. Books count: 0

B. Books count: 2

C. Books count: 1

D. Compilation error

Solution

1. Step 1: Understand @Query and modelContext.insert

   The @Query property fetches all Book entities. Inserting a new Book updates the data source.

2. Step 2: Check the effect of insertion on books.count

   After inserting one new Book, the count increases by 1, so it will be 1.

3. Final Answer:

   Books count: 1 -> Option C

4. Quick Check:

   Insert one book, count updates to 1 [OK]

Hint: Inserting updates @Query results immediately [OK]

Common Mistakes:

• Assuming count stays 0 after insert
• Expecting count to be 2 without adding twice
• Thinking code causes compile error

4. Identify the error in this SwiftData update code snippet:

func updateBookTitle(book: Book, newTitle: String) {
  book.title = newTitle
  modelContext.save()
}

medium

A. No error; code updates title correctly

B. Missing call to modelContext.insert(book)

C. book.title cannot be changed directly; must create new Book

D. modelContext.save() is not a valid method in SwiftData

Solution

1. Step 1: Check SwiftData update pattern

   In SwiftData, changes to model object properties are tracked automatically, but modelContext.save() is not a valid method to persist changes explicitly.

2. Step 2: Identify if there's an error

   Directly mutating book.title is correct, but calling modelContext.save() causes an error because the method does not exist.

3. Final Answer:

   modelContext.save() is not a valid method in SwiftData -> Option D

4. Quick Check:

   Property change tracked automatically; no save() method = A [OK]

Hint: SwiftData tracks changes automatically; no save() method needed [OK]

Common Mistakes:

• Thinking modelContext.save() exists
• Believing properties are immutable
• Confusing update with insert

5. You want to delete all Book objects with an empty title using SwiftData. Which code snippet correctly performs this operation?

hard

A. books.filter { $0.title.isEmpty }.forEach { modelContext.delete($0) }

B. for book in books where book.title.isEmpty { modelContext.delete(book) }

C. modelContext.deleteAll(Book.self, where: \"title == ''\")

D. modelContext.remove(books.filter { $0.title.isEmpty })

Solution

1. Step 1: Understand deletion in SwiftData

   To delete objects, you call modelContext.delete(object) for each object.

2. Step 2: Check each option for correctness

   books.filter { $0.title.isEmpty }.forEach { modelContext.delete($0) } filters books with empty titles and deletes each correctly. for book in books where book.title.isEmpty { modelContext.delete(book) } syntax is invalid in Swift. modelContext.deleteAll(Book.self, where: \"title == ''\") uses a non-existent method. modelContext.remove(books.filter { $0.title.isEmpty }) uses wrong method name.

3. Final Answer:

   books.filter { $0.title.isEmpty }.forEach { modelContext.delete($0) } -> Option A

4. Quick Check:

   Filter then delete each = A [OK]

Hint: Filter then delete each object individually [OK]

Common Mistakes:

• Using invalid for-in with where clause
• Calling non-existent deleteAll method
• Using wrong method name like remove