Overloading the Extraction Operator
The extraction operator is defined for all the C++ and DB Interface Module data types. Naturally, it is easy to define it for your own classes. For example:
struct Purchase {
int videoID;
int supplierID;
int purchaseOrderNumber;
RWDecimalPortable pricePerUnit;
int quantity;
RWDateTime date;
};
RWDBReader&
operator>>(RWDBReader& rdr, Purchase& p) {
rdr >> p.videoID >> p.supplierID
>> p.purchaseOrderNumber
>> p.pricePerUnit >> p.quantity >> p.date;
return rdr;
}
Now we can read from the purchase table directly into Purchase instances:
Purchase p;
while (rdr()) {
rdr >> p;
// process p;
}
This is an important technique, and it is explained more thoroughly in
Chapter 17, Retrieving Data from a Table, the first advanced tutorial.
