struct LoginCredentials: Codable {
    let login: String
    let password: String
    
    init(login: String, password: String) {
        self.login = login
        self.password = password
    }
    
    func validate() -> Result<LoginCredentials> {
        let valid = login.count > 3 && password.count > 6
        return valid ? Result(value: self) : Result(error: .invalidLoginCredentials)
    }
}

LoginCredentials.validate()