‘ref’ is not a member of ‘vmime’

[dimkaip]

Hi Vincent.
I am completely new to VMime.
Working with bellow code vmime works fine... I am in mint Linux and CodeBlocks.
class myObject: public vmime::object {
private: vmime::string m_name;
public: myObject(const vmime::string& name) : m_name(name) {}
void sayHello() {
std::cout << "Hello " << m_name << endl;
}
};
vmime::shared_ptr obj = vmime::make_shared("World!");
obj->sayHello();

But in sample
vmime::utility::url url("smtp://smtp.gmail.com");
vmime::ref vmime::net::transport tr = session->getTransport(url);
tr->setProperty("connection.tls", true);
...........
i am getting error ‘ref’ is not a member of ‘vmime’
Why is that?
Thank you
Jim