Article
Classes
The type of an object is known as its class. A
class is an abstract representation, or, metaphorically speaking, a set
of instructions for building objects. So that you can describe the
properties of objects, classes contain
components , which define the state and
behavior of objects.
Global and Local Classes
You can define classes globally
in the class library in the repository or
locally in an ABAP program.
Global classes are coded in a special
ABAP program, a Class-Pool , whereas
local classes can be coded in almost
every ABAP program. Global classes are visible in all ABAP programs. The
usablity depends on the package check. Local classes can only be used
statically in their own program. Dynamic accesses are also possible
across program limits but it is not recommended. When a global class is
used for the first time, the class pool is loaded into the
internal session of the user. The
local classes of a class pool can be used by the pool's global classes.
Except for the storage type and the visibility, there are hardly any
conceptual differences between global and local classes. One of the few
differences is that in the public interface of a global class only
references to public types are possible. These types are subdivided into
global and local friends .
In principle, it also does not make any difference if you call a method
of a local or global class. This is the reason why classes that are used
by several programs are exclusively created in the class library. You
should avoid, if possible, to reuse local classes using
include programs .
Documentation extract taken from SAP system, � Copyright SAP AG. All rights reserved