ABAP_to_the_Future

10
ALV SALV Reporting Framework
10.2 Designing a Report Interface
Now that you’ve defined an SALV-specifi c class and coded the program to call a
report, you’ll create an interface for the concrete class to implement. This interface
is the public API for disparate re port technologies; the calling program
knows what the report technology can give it and cares not how it’s achieved.
An interface is composed of attribute definitions and method definitions. The
attribute definition section of the interf ace contains very little (in fact, nothing)
we can include that is statically typed; each technology uses very different structures
(or objects) to get the job done. In fact, the only thing we can say for certain
is that there will always be a table of data to be displayed, and it will be defined
differently in every case.
Interface methods are supposed to be an abstract representation of tasks in a
high-level process—in this case, the pr ocess a program has to go through when
preparing and displaying a report. Therefore, in order to know what method definitions
to create, you need to think of the high-level steps (Figure 10.2) executed
by the calling program when a report is executed.
Create Container
(Optional)
Initialize
(Generic)
Application-Specific
Changes
(Specific)
Display
(Generic)
Figure 10.2 Steps in Report Execution
As you can see in Figure 10.2, there are four high-level steps executed by the program.
Once designed, the interface will re present this high-level view expressed
in SAP terms. The calling report will only know about this high-level framework.
Classes specific to each UI technology will determine how to implement each
step, thus separating the “what” from the “how to.”
Note
The designation of “Specific” or “Generic ” in parentheses in Figure 10.2 refers to
whether or not each step requires that you write unique code for an individual program.
Logically, application-specific changes must be written differently for each individual
program. All the other steps are generic, which mean they apply to every single report
you create.
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