title: Convert a QVariant of a custom type to a QString
body: <p>I have a custom class called Money that I have declared with Q_DECLARE_METATYPE().</p>
  
  <pre><code>class Money {
  public:
    Money(double d) {
      _value = d;
    }
    ~Money() {}
    QString toString() const {
      return QString(_value);
    }
  private:
    double _value;
  };
  Q_DECLARE_METATYPE(Money);
  
  Money m(23.32);
  </code></pre>
  
  <p>I store that in a QVariant and I want to convert it to a QString:</p>
  
  <pre><code>QVariant v = QVariant::fromValue(m);
  
  QString s = v.toString();
  </code></pre>
  
  <p>Variable <strong>s</strong> ends up being a null string because QVariant doesn't know how to convert my custom type to the string. Is there any way to do this?</p>