ABAP_to_the_Future

7
Exception Classes and Design by Contract
lo_monster ?= data_object.
result = abap_false.
CHECK lo_monster->scariness CS 'SCARY'.
CHECK lo_monster->bolts_in_neck EQ 2.
CHECK lo_monster->fluffiness EQ 0.
CHECK lo_monster->colour NE 'PINK'.
result = abap_true.
ENDMETHOD.
"IF_CONSTRAINT~is_valid
METHOD if_constraint~get_description.
*-------------------------------------------------------*
* RETURNING result TYPE string_table
*-------------------------------------------------------*
* Local Variables
DATA: ld_message TYPE string.
ld_message = 'Monster is no longer a monster!'.
APPEND ld_message TO result.
ENDMETHOD. "IF_CONSTRAINT~get_description
ENDCLASS. "Monster Constraint Implementation
Listing 7.13 Pink and Fluffy is not Scary!
You could then add the code in Listing 7.14 to the end of every method in the
monster class. In this way, you can be sure that no method call will have an
adverse effect on the essential nature of the monster.
zcl_dbc=>ensure(
that = 'The Monster is still a Monster'
which_is_true_if = lo_monster_constraint->if_constraint~is_valid( mo_
class_under_test ) ).
Listing 7.14 Calling a Class Invariant at the End of Each Method Call
Note
Instead of adding the code in Listing 7.14 to the end of every method call, you could
alternatively add such a call to the end of every unit test you do on the monster class. It
would not make much sense to do both.
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