This regular expression is adapted from a version at regular-expressions.info and is a complete verification of RFC 2822. Source: http://www.cocoawithlove.com/2009/06/verifying-that-string-is-email-address.html. Dedicate article: https://medium.com/@darthpelo/email-validation-in-swift-3-0-acfebe4d879a

EmailValidator.swift

extension String {
    
    /// Checks if the `String` is a valid email address.
    /// ````
    /// // Example
    /// "[email protected]".isValidEmailAddress() // true
    /// "name(at)email(dot)com".isValidEmailAddress() // false
    /// "name@email".isValidEmailAddress() // false
    /// "[email protected]".isValidEmailAddress() // false
    /// "name.com".isValidEmailAddress() // false
    /// ````
    /// - Note: GitHubGist: [darthpelo/EmailValidator.swift](https://gist.github.com/darthpelo/dfe3c460585f4f035c24ede994faeb80#file-emailvalidator-swift)
    func isValidEmailAddress() -> Bool {
        let emailRegEx = "(?:[a-zA-Z0-9!#$%\\&‘*+/=?\\^_`{|}~-]+(?:\\.[a-zA-Z0-9!#$%\\&'*+/=?\\^_`{|}"
            + "~-]+)*|\"(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21\\x23-\\x5b\\x5d-\\"
            + "x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])*\")@(?:(?:[a-z0-9](?:[a-"
            + "z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\\[(?:(?:25[0-5"
            + "]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-"
            + "9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21"
            + "-\\x5a\\x53-\\x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])+)\\])"
        
        let emailTest = NSPredicate(format:"SELF MATCHES[c] %@", emailRegEx)
        return emailTest.evaluate(with: self)
    }
}