Saturday, June 23
Function groups and now Objects in the new ABAP Objects language
The center of
ABAP Objects are Objects. Any object oriented language focuses on objects and
hence maps objects with the real world entities. After release 3.1 of SAP WAS
ABAP, BOR or the business object repository contains objects. Examples of
objects are customers, invoice, order etc. These are contained in the BOR as
examples.
Function Groups
and function modules were like objects in ABAP versions before ABAP objects was
introduced. Function groups contain function modules. FMs can be treated as
services or functions of the objects. Also the global data of function groups
formed the attributes of the objects. For example: an FG which processes Sales
orders has many FMs within it and global data declared. Global data can be
accessed by the FMs within the FG. This ensures encapsulation. The data (global
data) and the services (FMs) are combined within a FG.
ABAP programs
hold a specific amount of memory art runtime. Similarly when a FM is called, it
loads its corresponding FG and global data into memory. One ABAP program can
call multiple FMs from several FGs and hence multiple internal ABAP sessions
can run and memory occupied.
As already
said, When a FM is called, its FG with global data is loaded into memory. This
instance of FG can be treated as Object when we look at this from the Object
orientation perspective. So the instance of function group is an interface
between the user and function module. Function groups global data can be
accessed via function modules only. If Function groups and function modules can
be used for object orientation of a program then why ABAP Objects was introduced?
The answer is below.
In classical
ABAP, a program can work with many instances of different function groups.
But it is not
possible to work on many instances of a single function group at a time.
ABAP Objects
allow the user to work with many instances of a class.
For example :
You are supposed to develop a ABAP program which can process many sales orders
at the same time. It is not possible to do so with function groups philosophy.
You would instead need a class and several objects of that class. Each object at
that time would represent a Sales Order.
So now with the
new ABAP objects, you can load multiple instances of the same Class using
CREATE OBJECT statement. ABAP accesses the interface of the instance using
Object’s reference.
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