13.1.18 Implementing Operations

The signature of an implementation member function is the mapped signature of the OMG IDL operation. Unlike the client side, the server-side mapping requires that the function header include the appropriate exception (throw) specification. This requirement allows the compiler to detect when an invalid exception is raised, which is necessary in the case of a local C++-to-C++ library call (otherwise, the call would have to go through a wrapper that checks for a valid exception). For example:

// IDL
interface A
{
exception B {};
void f() raises(B);
};
// C++
class MyA : public virtual POA_A
{
  public:
void f() throw(A::B, CORBA::SystemException);
...
};

Since all operations and attributes may throw CORBA system exceptions, CORBA::SystemException must appear in all exception specifications, even when an operation has no raises clause.

Within a member function, the “this” pointer refers to the implementation object’s data as defined by the class. In addition to accessing the data, a member function may implicitly call another member function defined by the same class. For example:

// IDL
interface A
{
void f();
void g();
};
// C++
class MyA : public virtual POA_A
{
  public:
void f() throw(SystemException);
void g() throw(SystemException);
  private:
long x_;
};

void
MyA::f() throw(SystemException)
{
this->x_ = 3;
this->g();
}

However, when a servant member function is invoked in this manner, it is being called simply as a C++ member function, not as the implementation of an operation on a CORBA object. In such a context, any information available via the POA_Current object refers to the CORBA request invocation that performed the C++ member function invocation, not to the member function invocation itself.

• Skeleton Derivation from Object