How to make simple form validator in Swift

class Validator {
    func validate(text: String, with rules: [Rule]) -> String? {
        return rules.compactMap({ $0.check(text) }).first
    }

    func validate(input: InputView, with rules: [Rule]) {
        guard let message = validate(text: input.textField.text ?? "", with: rules) else {
            input.messageLabel.isHidden = true
            return
        }

        input.messageLabel.isHidden = false
        input.messageLabel.text = message
    }
}

struct Rule {
    // Return nil if matches, error message otherwise
    let check: (String) -> String?

    static let notEmpty = Rule(check: {
        return $0.isEmpty ? "Must not be empty" : nil
    })

    static let validEmail = Rule(check: {
        let regex = #"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,64}"#

        let predicate = NSPredicate(format: "SELF MATCHES %@", regex)
        return predicate.evaluate(with: $0) ? nil : "Must have valid email"
    })

    static let countryCode = Rule(check: {
        let regex = #"^\+\d+.*"#

        let predicate = NSPredicate(format: "SELF MATCHES %@", regex)
        return predicate.evaluate(with: $0) ? nil : "Must have prefix country code"
    })
}

let validator = Validator()
validator.validate(input: inputView, with: [.notEmpty, .validEmail])

class ValidatorTests: XCTestCase {
    let validator = Validator()

    func testEmpty() {
        XCTAssertNil(validator.validate(text: "a", with: [.notEmpty]))
        XCTAssertNotNil(validator.validate(text: "", with: [.notEmpty]))
    }

    func testEmail() {
        XCTAssertNil(validator.validate(text: "onmyway133@gmail.com", with: [.validEmail]))
        XCTAssertNotNil(validator.validate(text: "onmyway133", with: [.validEmail]))
        XCTAssertNotNil(validator.validate(text: "onmyway133.com", with: [.validEmail]))
    }

    func testCountryCode() {
        XCTAssertNil(validator.validate(text: "+47 11 222 333", with: [.countryCode]))
        XCTAssertNotNil(validator.validate(text: "11 222 333", with: [.countryCode]))
        XCTAssertNotNil(validator.validate(text: "47 11 222 333", with: [.countryCode]))
    }
}