ABAP_to_the_Future

9
BRFplus
Here, there is only one result allowed, so if you have multiple values coming back
(the exception rather than the rule, you would think), then you have to define the
result object as a structure or a table rather than a data element. Do this by defining
a structure or a table type using SE11, and then set the type of the result data
object to be that DDIC structure or table. In Figure 9.10, you’ll see the completed
signature—input and output parameters —of your function; i.e., everything
below Context.
Now that you have a means to receive some data and send back a result, it’s time
to move on to the next level down, whic h is a ruleset. You could ask me what a
ruleset is, and I could answer that it’s a set of rules, but probably that would not
make you any better off. The best way of answering is by way of an example. In
this example, one of the monsters has been arrested for not killing enough peasants.
The sentence is destruction. The baron launches a legal appeal based on the
laws of Transylvania—an enormous set of legal rules built up over many centuries.
The judge cannot come to a decision, so th e case is referred to the court of the
European Union, where another judge wi ll consider the matter based on European
laws. That judge cannot come to a decision either, so the case is referred to
the United Nations to be tried under inte rnational law. This time, a decision is
made, and the monster is released on the condition that it does better next time.
In this case, the first (Transylvanian) set of rules cannot come back with a result,
so another attempt is made with a different (European) set of rules, which also produces
no result, and so a third (international) set of rules is invoked, which does
produce a result. In every case, the input data—the facts of the case—was the same.
The BRFplus equivalent of our real-life example is that a BRFplus function can have
many rulesets, and each ruleset can have one or many rules; the idea is to loop
through the rulesets until you get a result. If a certain set of rules is unable to make
a decision, then instead of giving up you can try a totally different strategy, by passing
a new set of rules the same input data to see if they can do a better job.
Just to keep this simple for the moment, there will be one ruleset with one rule.
Both the ruleset and the rule have the simple job of determining what type of
ingredients to use for a monster based on the customer requirements. In order to
create a ruleset, navigate from the Signature tab of the function to the Assigned
Rulesets tab; the screen will now look like Figure 9.11.
370