Nil represents absence of value in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Swift code using nil?

Consider this Swift code snippet. What will it print?

Swift

var name: String? = nil
if name == nil {
    print("No name provided")
} else {
    print("Name is \(name!)")
}

A Compilation error

B Name is nil

C Name is Optional(nil)

D No name provided

💡 Hint

Think about what happens when you compare an optional variable to nil.

The variable 'name' is an optional String set to nil. The if condition checks if name is nil, which is true, so it prints 'No name provided'.

❓ Predict Output

intermediate

What happens when you force unwrap a nil optional?

What will happen when this Swift code runs?

Swift

var number: Int? = nil
print(number!)

A Runtime crash due to force unwrapping nil

B Prints nil

C Prints 0

D Compilation error

💡 Hint

Force unwrapping nil causes a runtime error.

Trying to force unwrap an optional that is nil causes a runtime crash with a fatal error.

🧠 Conceptual

advanced

Which statement about nil in Swift is true?

Choose the correct statement about nil in Swift.

A nil is the same as an empty string for String variables

B nil can be assigned to any variable type

C nil represents the absence of a value only for optional types

D nil can be used to reset non-optional variables

💡 Hint

Think about which types can hold nil values.

In Swift, only optional types can hold nil to represent absence of a value. Non-optional types cannot be nil.

❓ Predict Output

advanced

What is the output of this optional binding code?

What will this Swift code print?

Swift

var age: Int? = nil
if let actualAge = age {
    print("Age is \(actualAge)")
} else {
    print("Age is not set")
}

A Compilation error

B Age is not set

C Age is nil

D Age is 0

💡 Hint

Optional binding only runs the if block if the optional has a value.

Since age is nil, the else block runs and prints 'Age is not set'.

❓ Predict Output

expert

What is the output of this Swift code with nil coalescing?

What will this Swift code print?

Swift

var city: String? = nil
let displayCity = city ?? "Unknown"
print(displayCity)

A Unknown

B nil

C Compilation error

D Optional(nil)

💡 Hint

The nil coalescing operator provides a default value if the optional is nil.

Since city is nil, the nil coalescing operator returns the default string 'Unknown'.