Protocol conformance in Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a protocol named Printable.

Swift

protocol [1] {
    func printDetails()
}

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

APrintableType

BPrintableProtocol

CPrint

DPrintable

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different protocol name than Printable.

Adding extra words like 'Protocol' in the name.

The protocol is named Printable. This name matches the usage in the code.

2fill in blank

medium

Complete the code to make the struct conform to the Printable protocol.

Swift

struct User: [1] {
    var name: String
    func printDetails() {
        print("User: \(name)")
    }
}

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

APrintableProtocol

BPrintableType

CPrintable

DPrint

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong protocol name.

Forgetting to add the protocol after the colon.

The struct User conforms to the Printable protocol by declaring it after the colon.

3fill in blank

hard

Fix the error by completing the method to conform to Printable.

Swift

struct Product: Printable {
    var id: Int
    func [1]() {
        print("Product ID: \(id)")
    }
}

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

AprintDetails

BshowDetails

Cdisplay

DprintInfo

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different method name than required.

Missing the method implementation.

The method name must be printDetails() to match the protocol requirement.

4fill in blank

hard

Fill both blanks to create a protocol and make a class conform to it.

Swift

protocol [1] {
    func describe()
}

class Car: [2] {
    func describe() {
        print("This is a car.")
    }
}

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

ADescribable

BPrintable

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for protocol and conformance.

Using the wrong protocol name.

The protocol is named Describable and the class Car conforms to it by declaring Describable.

5fill in blank

hard

Fill all three blanks to define a protocol with a property and method, then conform a struct to it.

Swift

protocol [1] {
    var name: String { get }
    func greet()
}

struct Person: [2] {
    var name: String
    func [3]() {
        print("Hello, \(name)!")
    }
}

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

AGreetable

Cgreet

DgreetDetails

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for protocol and conformance.

Incorrect method name implementation.

The protocol is named Greetable. The struct Person conforms to it and implements the method greet().

Practice

1. What does it mean for a Swift type to conform to a protocol?

easy

A. It can only be a class, not a struct or enum.

B. It inherits all properties and methods from the protocol automatically.

C. It implements all required methods and properties defined by the protocol.

D. It must override all methods from the protocol.

Solution

1. Step 1: Understand protocol requirements

   A protocol defines methods and properties that a type must implement to conform.

2. Step 2: Check what conformance means

   Conforming means the type provides implementations for all required members.

3. Final Answer:

   It implements all required methods and properties defined by the protocol. -> Option C

4. Quick Check:

   Protocol conformance = Implement required members [OK]

Hint: Conformance means implementing all required protocol parts [OK]

Common Mistakes:

• Thinking conformance means inheritance
• Believing only classes can conform
• Assuming methods must be overridden

2. Which of the following is the correct syntax to declare that a struct conforms to a protocol named Drawable?

easy

A. struct Shape inherits Drawable { }

B. struct Shape : Drawable { }

C. struct Shape implements Drawable { }

D. struct Shape extends Drawable { }

Solution

1. Step 1: Recall Swift syntax for protocol conformance

   Swift uses a colon (:) after the type name to declare protocol conformance.

2. Step 2: Match syntax options

   Only struct Shape : Drawable { } uses the correct colon syntax for protocol conformance.

3. Final Answer:

   struct Shape : Drawable { } -> Option B

4. Quick Check:

   Protocol conformance syntax uses ':' [OK]

Hint: Use ':' after type name to conform to protocol [OK]

Common Mistakes:

• Using 'implements' or 'inherits' keywords
• Confusing inheritance with protocol conformance
• Using 'extends' which is not Swift syntax

3. What will be the output of this Swift code?

protocol Greetable {
    func greet() -> String
}

struct Person: Greetable {
    func greet() -> String {
        "Hello!"
    }
}

let p = Person()
print(p.greet())

medium

A. Hello!

B. Error: Missing greet() implementation

C. nil

D. Hello! Person

Solution

1. Step 1: Check protocol and struct conformance

   The protocol requires a greet() method returning String. Person implements greet() returning "Hello!".

2. Step 2: Analyze print output

   Calling p.greet() returns "Hello!", so print outputs that string.

3. Final Answer:

   Hello! -> Option A

4. Quick Check:

   Implemented greet() returns "Hello!" [OK]

Hint: Implemented method returns string printed directly [OK]

Common Mistakes:

• Assuming missing implementation error
• Expecting default protocol method output
• Confusing print output with type description

4. Identify the error in this Swift code that tries to conform to the Equatable protocol:

struct Point: Equatable {
    var x: Int
    var y: Int
}

medium

A. Missing implementation of == operator function

B. Struct cannot conform to Equatable

C. Properties must be constants (let) to conform

D. No error, code compiles fine

Solution

1. Step 1: Understand Equatable conformance rules

   Swift automatically synthesizes == for structs with Equatable properties.

2. Step 2: Check struct properties and conformance

   Both x and y are Int (Equatable), so compiler provides == automatically.

3. Final Answer:

   No error, code compiles fine -> Option D

4. Quick Check:

   Automatic Equatable synthesis = No error [OK]

Hint: Swift auto-synthesizes Equatable for simple structs [OK]

Common Mistakes:

• Thinking manual == is always needed
• Believing structs can't conform
• Assuming properties must be let

5. Given this protocol and struct, how can you modify Vehicle to conform to CustomStringConvertible and print a description?

protocol CustomStringConvertible {
    var description: String { get }
}

struct Vehicle {
    var make: String
    var model: String
}

hard

A. Add extension Vehicle: CustomStringConvertible { var description: String { "\(make) \(model)" } }

B. Add func description() -> String { return "\(make) \(model)" } inside Vehicle

C. Add var description: String = "\(make) \(model)" inside Vehicle

D. Add override var description: String { "\(make) \(model)" } inside Vehicle

Solution

1. Step 1: Understand protocol property requirement

   CustomStringConvertible requires a read-only computed property 'description' of type String.

2. Step 2: Implement description correctly

   Implementing description as a computed property in an extension is the correct way.

3. Final Answer:

   Add extension Vehicle: CustomStringConvertible { var description: String { "\(make) \(model)" } } -> Option A

4. Quick Check:

   Computed property in extension = Correct conformance [OK]

Hint: Use computed property in extension for protocol conformance [OK]

Common Mistakes:

• Trying to add description as a method
• Using stored property instead of computed
• Using override keyword in struct