Identifiable protocol in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to make the struct conform to the Identifiable protocol by adding the required property.

iOS Swift

struct User: Identifiable {
  var [1]: Int
  var name: String
}

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

Aid

Bname

Cidentifier

Duid

Attempts:

3 left

💡 Hint

Common Mistakes

Using a property name other than 'id'.

Forgetting to add the 'id' property.

The Identifiable protocol requires a property named id to uniquely identify the instance.

2fill in blank

medium

Complete the code to conform to Identifiable using a UUID as the id.

iOS Swift

struct Item: Identifiable {
  var [1] = UUID()
  var title: String
}

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

Auuid

Bidentifier

Cid

DitemId

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different property name like 'uuid' or 'identifier'.

Not initializing the id property.

The id property is required by Identifiable and can be assigned a UUID for uniqueness.

3fill in blank

hard

Fix the error in the struct by adding the missing Identifiable requirement.

iOS Swift

struct Product: Identifiable {
  var name: String
  var price: Double
  var [1]: Int
}

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

Auid

BproductId

Cidentifier

Did

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different property name.

Not adding the id property at all.

The Identifiable protocol requires a property named id. Adding it fixes the error.

4fill in blank

hard

Fill both blanks to create a struct conforming to Identifiable with a UUID id and a title.

iOS Swift

struct Task: Identifiable {
  var [1] = UUID()
  var [2]: String
}

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

Aid

Btitle

Cname

Duuid

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'uuid' instead of 'id' for the identifier.

Using 'name' instead of 'title' for the descriptive property.

The id property is required by Identifiable and is set to a UUID. The title is a descriptive property.

5fill in blank

hard

Fill all three blanks to define a struct conforming to Identifiable with a UUID id, a name, and a description.

iOS Swift

struct Event: Identifiable {
  var [1] = UUID()
  var [2]: String
  var [3]: String
}

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

Aid

Bname

Cdescription

Dtitle

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'title' instead of 'name' or 'description'.

Not using 'id' as the identifier property.

The id property is required by Identifiable. The name and description provide details about the event.

Practice

1.

What is the main purpose of the Identifiable protocol in Swift?

easy

A. To enforce a specific initializer

B. To make a class inherit from another class

C. To add default methods to a struct

D. To require a unique id property for each instance

Solution

1. Step 1: Understand the Identifiable protocol

   The Identifiable protocol requires that a type has a unique id property.

2. Step 2: Identify the purpose of the id

   This unique id helps SwiftUI distinguish between different instances, especially in lists.

3. Final Answer:

   To require a unique id property for each instance -> Option D

4. Quick Check:

   Identifiable = unique id required [OK]

Hint: Identifiable means each item must have a unique id [OK]

Common Mistakes:

• Thinking it adds methods instead of requiring an id
• Confusing it with inheritance
• Assuming it enforces initializers

2.

Which of the following is the correct way to declare a struct conforming to Identifiable with a constant id of type UUID?

struct Item: Identifiable {
    // Fill in the blank
}

easy

A. let id: UUID = UUID()

B. var id: UUID

C. var id = UUID()

D. func id() -> UUID

Solution

1. Step 1: Check property declaration for id

   The id must be a property, not a function.

2. Step 2: Choose correct syntax with initialization

   Using let id: UUID = UUID() declares a constant id initialized with a new UUID, which is correct.

3. Final Answer:

   let id: UUID = UUID() -> Option A

4. Quick Check:

   Property with UUID value, not function [OK]

Hint: id must be a property, not a function [OK]

Common Mistakes:

• Declaring id as a function
• Not initializing id
• Using var without initialization

3.

Given the code below, what will be printed?

struct User: Identifiable {
    let id: Int
    let name: String
}

let users = [User(id: 1, name: "Anna"), User(id: 2, name: "Ben")]
print(users[1].id)

medium

A. 1

B. Anna

C. 2

D. Ben

Solution

1. Step 1: Identify the second user in the array

   Index 1 refers to the second element, which is User(id: 2, name: "Ben").

2. Step 2: Access the id property

   The id of this user is 2, so print(users[1].id) prints 2.

3. Final Answer:

   2 -> Option C

4. Quick Check:

   Second user's id = 2 [OK]

Hint: Array index 1 is second element, check its id [OK]

Common Mistakes:

• Confusing index 0 and 1
• Printing name instead of id
• Assuming id is name

4.

What is wrong with this struct conforming to Identifiable?

struct Product: Identifiable {
    let name: String
}

medium

A. Missing id property required by Identifiable

B. The name property should be var, not let

C. Structs cannot conform to protocols

D. The struct must inherit from a class

Solution

1. Step 1: Check protocol requirements

   The Identifiable protocol requires a unique id property.

2. Step 2: Verify struct properties

   This struct only has name, no id property is declared.

3. Final Answer:

   Missing id property required by Identifiable -> Option A

4. Quick Check:

   Identifiable needs id property [OK]

Hint: Identifiable always needs an id property [OK]

Common Mistakes:

• Thinking name property suffices
• Believing structs can't conform to protocols
• Assuming var vs let matters here

5.

You want to create a list of tasks where each task has a unique string identifier. Which of the following struct definitions correctly conforms to Identifiable and uses a string id?

struct Task: Identifiable {
    let id: String
    let title: String

    init(title: String) {
        // Fill in the blank
    }
}

hard

A. self.title = title
self.id = title

B. self.title = title
self.id = UUID().uuidString

C. self.title = title
self.id = String()

D. self.title = title
self.id = nil

Solution

1. Step 1: Understand the need for unique string id

   The id must be unique for each task and of type String.

2. Step 2: Check each option for uniqueness and type

   self.title = title self.id = UUID().uuidString uses UUID().uuidString which generates a unique string each time, fulfilling the requirement.

3. Final Answer:

   self.title = title self.id = UUID().uuidString -> Option B

4. Quick Check:

   Unique string id = UUID().uuidString [OK]

Hint: Use UUID().uuidString for unique string ids [OK]

Common Mistakes:

• Using title as id which may not be unique
• Assigning empty string as id
• Setting id to nil which is invalid