Using Caché Objects - InterSystems Documentation

Relationships
Do company.Employees.Insert(emp)
Write emp.TheCompany.Name
// this will print out "Chiaroscuro LLC"
You can load relationships from disk and use them as you would any other property. When
you refer to a related object from the ONE side, the related object is automatically swizzled
into memory in the same way as a reference (object-valued) property. When you refer to a
related object from the MANY side, the related objects are not swizzled immediately; instead
a transient %RelationshipObject collection object is created. As soon as any methods are called
on this collection, it builds a list containing the ID values of the objects within the relationship.
It is only when you refer to one of the objects within this collection that the actual related
object is swizzled into memory.
Here is an example that displays all Employee objects related to a specific Company:
// open an instance of Company
Set company = ##class(Company).%OpenId(id)
// iterate over the employees; print their names
Set key = ""
Do {
Set employee = company.Employees.GetNext(.key)
If (employee '= "") {
Write employee.Name,!
}
} While (key '= "")
In this example, closing company removes the Company object and all of its related Employee
objects from memory. Note, however, that every Employee object contained in the relationship
will be swizzled into memory by the time the loop completes. To reduce the amount of
memory that this operation uses—perhaps there are thousands of Employee objects—then
modify the loop to “unswizzle” the Employee object after displaying the name, by calling
the %UnSwizzleAt method:
Do {
Set employee = company.Employees.GetNext(.key)
If (employee '= "") {
Write employee.Name,!
// remove employee from memory
Do company.Employees.%UnSwizzleAt(key)
}
} While (key '= "")
130 Using Caché Objects