CLASS_CONSTRUCTOR would be called automatically whenever the class would be accessed – either by creation of an instance or accessing any component. But seems like it is changed with ABAP 740.
Selection criteria object for the reports where you can implement the MVC for decoupling. This approach is using the FM RS_REFRESH_FROM_SELECTOPTIONS.
Lets checkout the ABAP object oriented approach for reports when you want to get data from different data sources – Database and/or Archive .
Gaining access to the object, when working with ABAP Objects Events, which raised the event would be an added advantage for the event handler method.