Object Views
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Object Relations Expressions

Open a view

In most cases we want to iterate over all objects of a certain type. How can we achieve this? We open a view for the type we want to inspect.

Again we use our little person class and insert some persons into our store.

// add some friends
ostore.insert(new person("joe"))
ostore.insert(new person("walter"));
ostore.insert(new person("helen"));
ostore.insert(new person("tim"));

Than we create a view with the oos::object_view class. This class takes as the template parameter the desired class type. Then we can use the view like a STL list containing oos::object_ptr of our desired type.

// shortcut to the person view
typedef oos::object_view<person> person_view_t;
person_view_t pview(ostore);
person_view_t::iterator i = pview.begin();
for (i; i != pview.end(); ++i) {
std::cout << i->name() << std::endl;
}

But this class can to somethig more for us. If we have a hierarchy of classes, we can create a view of the base type and easily iterate overall sub-types.

Look at the next example. We have a hierachy with the person class as base class and inherited from that we have classes student and employee. And again we create a view of type person to access all objects of type person including sub-types student and employee.

class student : public person { //... };
class employee : public person { //... };
oos::object_store ostore;
ostore.insert_prototype<person>("person");
ostore.insert_prototype<student, person>("student");
ostore.insert_prototype<employee, person>("employee");
typedef oos::object_view<person> person_view_t;
person_view_t pview(ostore);
person_view_t::iterator i = pview.begin();
for (i; i != pview.end(); ++i) {
std::cout << i->name() << std::endl;
}
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Object Relations Expressions