Data Validation in Swift (iOS/macOS): Libraries and Approaches

Data Validation in Swift (iOS/macOS): Libraries, Tools, and Practical Examples

Data validation is one of the key aspects of developing high-quality iOS and macOS applications. Without reliable input validation, users may encounter errors, incorrect interface behavior, or even crashes. In this article, we will explore the best libraries and approaches for data validation in Swift, along with specific code examples.

Why is Data Validation Needed?

Validation allows you to:

• Guarantee the correctness of input data (email, phone number, password).
• Prevent errors on the server side.
• Improve user experience through instant feedback.
• Enhance application security.

Popular Libraries for Validation in Swift

Today, there are several proven libraries that simplify data validation:

• Validated — a lightweight library with support for Combine and SwiftUI.
• SwiftValidator — one of the first libraries for validating text fields.
• Validator (by Adamwaite) — a simple and flexible tool with many built-in rules.
• Regex — not a library, but a built-in mechanism for working with regular expressions, often used for validation.

Example 1: Email Validation Using Regular Expression

The simplest way is to use NSRegularExpression or the built-in range(of:options:) method.

import Foundation

func isValidEmail(_ email: String) -> Bool {    let emailRegex = "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\\\.[A-Za-z]{2,64}"    let emailPredicate = NSPredicate(format: "SELF MATCHES %@", emailRegex)    return emailPredicate.evaluate(with: email)}

// Usageprint(isValidEmail("test@example.com")) // trueprint(isValidEmail("invalid-email"))    // false

Example 2: Password Validation (Length, Digits, and Special Characters)

Often, a password must contain at least 8 characters, at least one digit, and one special character.

func isValidPassword(_ password: String) -> Bool {    // Minimum 8 characters    guard password.count >= 8 else { return false }        // Check for a digit    let digitRegex = ".*[0-9]+.*"    let digitPredicate = NSPredicate(format: "SELF MATCHES %@", digitRegex)    guard digitPredicate.evaluate(with: password) else { return false }        // Check for a special character    let specialCharRegex = ".*[!@#$%^&*()_+\\\\-=\\\\[\\\\]{};':\\"\\\\\\\\|,./<>?]+.*"    let specialPredicate = NSPredicate(format: "SELF MATCHES %@", specialCharRegex)    guard specialPredicate.evaluate(with: password) else { return false }        return true}

print(isValidPassword("Pass123!")) // trueprint(isValidPassword("weak"))     // false

Example 3: Using the Validator Library (Adamwaite)

The Validator library provides a convenient syntax for chaining rules.

import Validator

let emailRule = ValidationRulePattern(pattern: EmailValidationPattern.standard, error: "Invalid email")let emailResult = "user@domain.com".validate(rule: emailRule)

switch emailResult {case .valid:    print("Email is valid")case .invalid(let errors):    print("Error: \\(errors.first?.message ?? "")")}

Example 4: Custom Validator for Age Verification

Sometimes you need to check that the user is above a certain age.

struct AgeValidator {    static func isValid(age: Int) -> Bool {        return age >= 18 && age <= 120    }}

// Usagelet userAge = 25if AgeValidator.isValid(age: userAge) {    print(