Writing Custom streamContents() Functions
For classes with complicated designs, the Serialization package includes macros that enable you to use custom code.
For example, your program might use a class that has a C++ array as a data member. You can pass C++ statements to the RW_WHEN_INPUT() macro in its body argument; the statements are executed only during an input operation. You can also pass C++ statements to the RW_WHEN_OUTPUT() macro in its body argument; these statements are executed only during an output operation.
Within custom code, the current object input stream can be referred to using the RW_INPUT_STREAM macro, and the current object output stream by the RW_OUTPUT_STREAM macro.
// examples\serial\other\residential.h
class residential : public real_property
{
RW_DECLARE_VIRTUAL_STREAM_FNS(residential)
RW_DECLARE_FRIEND_CTOR_METHOD(real_property, residential)
public:
residential()
: shown_(0), dates_shown_(0)
{}
residential(const RWCString& address, const RWCString& size,
unsigned long footage, unsigned long shown,
const RWDate* dates)
: real_property(address, size), footage_(footage),
shown_(shown), dates_shown_(0) {
shown_ = shown;
if (shown) {
dates_shown_ = new RWDate[shown];
for (size_t i = 0; i < shown; i++) {
dates_shown_[i] = dates[i];
}
}
}
~residential() {
delete [] dates_shown_;
}
bool operator== (const residential& prop) const {
return real_property::operator==(prop);
}
private:
long footage_;
long shown_;
RWDate *dates_shown_; // 1
};
The custom streamContents() function now looks like the following code sample:
// examples\serial\other\residential.cpp
RW_BEGIN_STREAM_CONTENTS(residential)
{
RW_STREAM_PARENT(real_property)
RW_STREAM_ATTR_MEMBER(footage, footage_)
RW_STREAM_ATTR_MEMBER(shown, shown_) //1
RW_WHEN_INPUT( {
if (shown_) {
delete dates_shown_;
dates_shown_ = new RWDate[shown_]; //2
}
for (unsigned long i = 0; i < shown_; i++) {
RW_INPUT_STREAM >> dates_shown_[i];
}
})
RW_WHEN_OUTPUT( {
for (unsigned long i = 0; i < shown_; i++) { //3
RW_OUTPUT_STREAM << dates_shown_[i];
}
})
}
RW_END_STREAM_CONTENTS
