Using Caché Objects - InterSystems Documentation

22
Dynamic Dispatch
Caché classes can include support for what is called “dynamic dispatch.” If dynamic dispatch
is in use and a program references a property or method that is not part of the class definition,
then a method (called a “dispatch method” ) is called that attempts to resolve the undefined
method or property. For example, dynamic dispatch can return a value for a property that is
not defined or it can invoke a method for a method that isn't implemented. The dispatch destination
is dynamic in that it does not appear in the class descriptor and is not resolved until
runtime.
22.1 How Dynamic Dispatch Happens
Caché makes a number of dispatch methods available that you can implement. Each of these
methods attempts to resolve an element that is missing under different circumstances.
If you implement a dispatch method, it has the following effects:
• During application execution, if Caché encounters an element that is not part of the
compiled class, it invokes the dispatch method to try to resolve the encountered element.
• The application code that uses the class does not do anything special to make this happen.
Caché automatically checks for the existence of the dispatch method and, if that method
is present, invokes it.
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