Guard for early exit pattern in Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Swift code using guard?

Consider the following Swift function that uses a guard statement. What will be printed when calling checkNumber(5)?

Swift

func checkNumber(_ num: Int) {
    guard num > 10 else {
        print("Number is too small")
        return
    }
    print("Number is big enough")
}

checkNumber(5)

A Number is big enough

B Number is too small

C No output

D Compilation error

💡 Hint

Remember guard checks a condition and exits early if false.

The guard statement checks if num > 10. Since 5 is not greater than 10, the else block runs, printing "Number is too small" and returning early.

❓ Predict Output

intermediate

What will this Swift function print when called with checkName(nil)?

Analyze the function below that uses guard to unwrap an optional String. What is the output of checkName(nil)?

Swift

func checkName(_ name: String?) {
    guard let unwrappedName = name else {
        print("No name provided")
        return
    }
    print("Hello, \(unwrappedName)!")
}

checkName(nil)

A No name provided

B Hello, !

C Runtime error

D Hello, nil!

💡 Hint

Guard unwraps optionals safely.

The guard statement tries to unwrap name. Since name is nil, the else block runs, printing "No name provided" and returning early.

🔧 Debug

advanced

Why does this Swift code cause a compile error?

Examine the code below. Why does it fail to compile?

Swift

func validateAge(_ age: Int?) {
    guard age != nil else {
        print("Age is missing")
        return
    }
    print("Age is \(age!)")
}

validateAge(nil)

A Missing return statement inside guard else block

B Cannot force unwrap optional age

C guard condition must be a boolean expression

D print statement syntax error

💡 Hint

Remember guard requires exiting the current scope in else.

The guard else block must exit the current scope (return, break, continue, throw). Here, it only prints but does not return, causing a compile error.

❓ Predict Output

advanced

What is the output of this Swift function using multiple guard statements?

Look at the function below. What will it print when called with processData(5, nil)?

Swift

func processData(_ x: Int?, _ y: Int?) {
    guard let a = x else {
        print("x is nil")
        return
    }
    guard let b = y else {
        print("y is nil")
        return
    }
    print("Sum is \(a + b)")
}

processData(5, nil)

A Sum is 5

B x is nil

C No output

D y is nil

💡 Hint

Each guard checks one optional and exits early if nil.

The first guard unwraps x successfully (5). The second guard finds y is nil, so it prints "y is nil" and returns early.

🧠 Conceptual

expert

Why is the guard statement preferred for early exit in Swift functions?

Choose the best explanation for why Swift developers use guard statements for early exit.

A Guard statements allow variables to be mutable inside the else block only.

B Guard statements automatically catch runtime errors without needing explicit error handling.

C Guard statements improve code readability by handling error cases early and reducing nested code blocks.

D Guard statements replace the need for if-else statements in all cases.

💡 Hint

Think about how guard affects code structure and clarity.

Guard statements help keep the main logic at the top level by exiting early on error or invalid conditions, reducing nested if-else blocks and improving readability.