Question

How to handle invalid argument in Swift

Answer 1

import Foundation

func checkNumber(_ num: Int) {
    guard num >= 0 else {
        print("Error: Negative numbers are not allowed.")
        return
    }
    print("Number: \(num)")
}

checkNumber(56)  // Works fine
checkNumber(-6)  // Prints error message




/*
run:

Number: 56
Error: Negative numbers are not allowed.

*/

 

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Answer 2

import Foundation

func validateAge(_ age: Int) {
    precondition(age >= 18, "Age must be 18 or older")
    print("Valid age: \(age)")
}

validateAge(19)  // Works fine
validateAge(14)  // Crashes in debug mode



/*
run:

Precondition failed: Age must be 18 or older: file Main.swift, line 2

*/

 

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Answer 3

import Foundation

enum ValidationError: Error {
    case invalidAge
}

func checkAge(_ age: Int) throws {
    if age < 18 {
        throw ValidationError.invalidAge
    }
    print("Valid age: \(age)")
}

do {
    try checkAge(15) // Throws error
} catch {
    print("Error: Invalid age (age < 18)")
}




/*
run:

Error: Invalid age (age < 18)

*/

 

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Answer 4

import Foundation

func safeDivide(_ a: Int, _ b: Int) -> Int? {
    guard b != 0 else { return nil }
    return a / b
}

if let result = safeDivide(34, 0) {
    print("Result: \(result)")
} else {
    print("Error: Division by zero.")
}




/*
run:

Error: Division by zero.

*/

 

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