ABAP_to_the_Future

Using BOPF to Write a DYNPRO-Style Program 8.2
Coding the Action
Now that the action has been created, you have to code it. The first step is to create
a public method for howling at the m oon. This will have a single importing
parameter that corresponds to the stru cture you defined when creating your
action in BOPF—namely, ZSA_HOWL_AT_THE_MOON. (You could have a totally different
signature if you wanted, because the BOPF-generated action class can adapt
the generated input structure to the sign ature of the model. This would be the
case if you were hooking up an already existing model class to BOPF.)
Because methods of a model class can do literally anything that can be imagined
(in real actions, you update the current state of the object, or save it to the database,
or send an instruction to an exte rnal system), you will just have a method
with a few lines of code that sends a message to the SAP GUI (Listing 8.15) in your
model class and will concentrate on how to call this from BOPF.
METHOD howl_at_the_moon.
DO is_howl_request-no_of_howls TIMES.
MESSAGE 'Ooooooooooooooooooooooooo' TYPE 'I'.
ENDDO.
ENDMETHOD. "Howl at the Moon
Listing 8.15 Coding the Howl at the Moon Action in the Model Class
With that piece of programming genius out of the way, it’s time to turn to coding
the generated action class. Th e generated class implements the /BOBF/IF_FRW_
ACTION interface, which gives you three methods:
왘 RETRIEVE DEFAULT PARAM
This method sends out a list of what input fields are needed to call the action.
It’s remotely possible that a calling application might need the structure of the
action input parameter for some reason. If the parameter structure keeps
changing dramatically (e.g., if in th e BOPF definition the DDIC type of the
input parameter structure is changed), then the calling program might want to
fill the parameter fields dynamically so that the calling program does not have
to change when the BOPF object changes the parameter. That isn’t very likely,
though. This method is optional.
왘 PREPARE
An action can be performed on more thanone object, and this method lets you
limit the number of objects the acti on is performed upon. The difference
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