Guard Classes Without Templates
If your compiler doesn't support templates, or your application can't use them, applying the guard class becomes more difficult, but not impossible. You must provide a class that can be locked for each object. For instance, to support
RWDBConnection, you must provide the following class:
class GuardRWDBConnection {
RWDBConnection& conn_;
public:
GuardRWDBConnection(const RWDBConnection& conn)
: conn_((RWDBConnection&)conn) { conn_.acquire(); }
~GuardRWDBConnection()
{ conn_.release(); }
};
This class can be used like the previous template version. Compare that code with the example below.
Example 20 – Using a guard class without templates
void doSomething(const RWDBConnection& conn)
{
// We’re going to use the connection so we’d better
// control access
GuardRWDBConnection guard(conn); // RWDBConnection supports the
// necessary interface.
// Do something on the connection.
// The mutex is released when the Guard instance goes out of
// scope.
}