Introduction to ABAP Objects1

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Copyright Siemens Business Services

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ABAP OBJECTS


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Global network

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Day 1 Introduction to OOPS

OOPS Principles

ABAP Objects

Inheritance

Exercise Programs

Day 2

Event Handling

Global classes

Advanced Concepts

Exercise Programs


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Procedural programming

Object-oriented programming

Aims of the ABAP Objects programming language

Contents:

Introduction


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Machine language

Assembler

Java

C++

ABAP Objects

ABAP

History of Programming Languages


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Object-Oriented ProgrammingObject-Oriented Programming

Procedural ProgrammingProcedural Programming

Introduction : Overview


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DataData DataData

DataData DataData

DataData Functions are defined independently

of data structures

Direct access to data

FunctionFunction

FunctionFunctionFunctionFunctionFunctionFunction

FunctionFunctionFunctionFunctionFunctionFunctionFunctionFunction

Procedural Programming


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TYPES: ...

DATA: ...

...

PERFORM f1 ...

CALL FUNCTION ...

...

FORM f1 ...

...

ENDFORM.

Data declaration

Main program

Call subroutines

Call function modules

Define subroutines

Structure of ABAP Program


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...

CALL FUNCTION A2 ...

...

CALL FUNCTION B1 ...

...

ABAP Program Function groups

Function group A

Function module A1

Function module A2

Function module A3

Data

Function group B

Function module B1

Function module B2Data

Working with Function Groups


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FUNCTION-POOL counter.

DATA: count TYPE I.

FUNCTION SET_COUNTER.

* Local interface IMPORTING VALUE(set_value)

count = set_value

ENDFUNCTION.

FUNCTION INCREMENT_COUNTER.

ADD 1 TO count.

ENDFUNCTION.

FUNCTION GET_COUNTER.

* Local interface EXPORTING VALUE(get_value)

get_value = count.

ENDFUNCTION.

Function Group as Counter : Example


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DATA: number TYPE I VALUE 3.

CALL FUNCTION SET_COUNTER EXPORTING set_value = number.

DO 4 TIMES.CALL FUNCTION INCREMENT_COUNTER.

ENDDO.

CALL FUNCTION GET_COUNTER IMPORTING get_value = number.

RITE: ..., number, ...

Function Group as Counter : Example


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Function group COUNTER

SET_COUNTER

INCREMENT_COUNTER

GET_COUNTER

COUNTER

1 counter Any number of counters

Several Instances of Function Group?


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Procedural ProgrammingProcedural Programming

Object-Oriented ProgrammingObject-Oriented Programming

Introduction : Overview


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Why OOPs


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Quality

of asoftware product

Correctness Robustness

Extensibility Re-usability

Overall Aims of Software Development

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OBJECTS


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Tree

House

Crane

Objects are an abstraction of the real world

Objects are units made up of data and of the

functions belonging to that data

Real worldModel

DataMethodMethod

Method

DataMethodMethod

MethodData

MethodMethod

Method

Boat

DataMethodMethod

Method

What are Objects?


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Classes

Classes describe objects. From a technical point of view, objects are

runtime instances of a class.

In other words Class is nothing but a template which carries DATA

and METHODS to access the DATA

Objects

Objects are instances of classes. They contain data and provides

services. The data forms the attributes of the object. The services

are known as methods (also known as operations or functions)


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Extensibility

Re-usability

The following aims are better supported:

Extensibility through

Polymorphism

Inheritance

Re-usability through

Classes Encapsulation

Inheritance

Strengths of Object-Oriented Approach


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Uniform language throughout thedevelopment process

All participants

In all phases

Reality is reflected in appropriate software concepts

Objects -> objects

Their state -> attributes

Their functions -> methods

Strengths of Object-Oriented Approach


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Longer development phase before first results ready

Paradigm break between object-oriented programs andProcedural Programming

Weaknesses of Object-Oriented Approach


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BOR

ABAP Objects

Class library

OO application OO application

Outlook


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As simple as possible

Only object-oriented concepts, that have provedthemselves in other object-oriented programminglanguages

More frequent use of type checks

ABAP Objects : Design Aims


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* ABAP Program

CLASS lcl airplane DEFINITION.

...

ENDCLASS.

...

TYPES: ...

DATA: ...

...

* ABAP Objects Program

DATA: counter TYPE i.

...

CREATE OBJECT ...

counter = counter + 1.

...

True, compatible extension of ABAP

ABAP Objects statements can be used in conventional

ABAP programs

ABAP statements can be used in ABAP Objects programs

ABAP Objects

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Questions ?


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Global network

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ObjectsObjects

ClassesClasses

AttributesAttributes

MethodsMethods

Instantiation, Garbage CollectorInstantiation, Garbage Collector

Working with ObjectsWorking with Objects

Further PrinciplesFurther Principles


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ObjectsObjects

ClassesClasses


MethodsMethods




Principles : Overview-1


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Private accessEncapsulation

As a rule, attributes

Attributes

Events

Attributes

Methods

Events

Plane ID: ID0057231

Length: 70 m

Weight: 30,000 kg

landed

Methods

flyland

Example: airplane

Public accessInterfaceAs a rule,methods, events

Name: LH Berlin

Object-1


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ObjectsObjects

ClassesClasses


MethodsMethods






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CLASS DEFINITION.

ENDCLASS.

CLASS IMPLEMENTATION.

ENDCLASS.

Definition part

The class components (for

example, attributes and methods)

are defined in this part.

Definition partThe class components (for

example, attributes and methods)

are defined in this part.

Implementation part

This part only contains the method

implementations.

Implementation part

This part only contains the methodimplementations.

Class : Blueprint of Object


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Global network

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1. Attributes or Data

Determine the state of the object

2. Methods

Determine the Behavior of the Object

Used to access the Attribute

3. Events

Determines the Actions you can perform


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ObjectsObjects

ClassesClasses


MethodsMethods






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lcl_airplane

name: LHweight: 30 000tank:

lcl_tank

Attribute types can have any kind of data type:

Elementary types:

C, I, P, STRING

TYPE REF TO (References to objects/interfaces)

Define your own types

Attributes


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CLASS DEFINITION.

...

TYPES: .

CONSTANTS: constant TYPE VALUE .

DATA: variable1 TYPE ,

variable2 TYPE,variable3 LIKE variable1,variable4 TYPE VALUE,

variable5 TYPE READ-ONLY,variable6 TYPE REF TO,variable7 TYPE REF TO .

CLASS-DATA: ...

ENDCLASS.

CLASS DEFINITION....

TYPES: .CONSTANTS: constant TYPE VALUE .

DATA: variable1 TYPE ,variable2 TYPE,

variable3 LIKE variable1,variable4 TYPE VALUE,

variable5 TYPE READ-ONLY,

variable6 TYPE REF TO,variable7 TYPE REF TO .

CLASS-DATA: ...

ENDCLASS.

Attributes : Syntax


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PUBLIC SECTION.

...

PRIVATE SECTION.

DATA: weight TYPE saplane-weight,

name TYPE string.

ENDCLASS.


PUBLIC SECTION.

...

PRIVATE SECTION.


name TYPE string.

ENDCLASS.


PUBLIC SECTION.

DATA: name TYPE string.

PRIVATE SECTION.

DATA: weight TYPE saplane-weight.

ENDCLASS.


PUBLIC SECTION.


PRIVATE SECTION.

DATA: weight TYPE saplane-weight.

ENDCLASS.

better

Public attributes

Can be viewed andchanged by all users andin all methods

Direct access

Private attributes

Can only be viewed andchanged from within theclass

No direct access

from outside the class

Attributes : Visibility


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PUBLIC SECTION.

PRIVATE SECTION.


name TYPE string.

CLASS-DATA: count TYPE I.

ENDCLASS.

Instance attributes

One per instance

Statement: DATA

Static attributes

Only one per class Statement: CLASS-DATA

Also known as class attributes

Attributes : Instance and Static-1


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Main

name: LH Berlin

weight: 30,000 kg

name: AA Boston

weight: 45,000 kg

count:

Static attributes for class LCL_AIRPLANE

Attributes : Instance and Static-2


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ObjectsObjects

ClassesClasses


MethodsMethods






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lcl_airplane

...

flyland

Contain coding

Have an interface

Methods


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CLASS IMPLEMENTATION.

ETHOD.

...

ENDMETHOD.

ENDCLASS.

CLASS DEFINITION.

...ETHODS:

[ IMPORTING TYPE EXPORTING TYPE

CHANGING TYPE RETURNING VALUE() TYPE EXCEPTIONS ].

ENDCLASS.

Methods : Syntax


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PUBLIC SECTION.ETHODS: set_name importing

im name TYPE string.

PRIVATE SECTION.

ETHODS: init name.


ENDCLASS.

CLASS lcl airplane IMPLEMENTATION.

ETHOD init name.

name = No Name.

ENDMETHOD.

ETHOD set_name.

IF im name IS INITIAL.

* Calling init name

...

ELSE. name = im name. ENDIF.

ENDMETHOD.ENDCLASS.

Public methods

Can be called fromoutside the class

Private methods

Can only be calledwithin the class

Methods : Visibility


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Instance methods

Can use both static and instance components in the implementation part

Can be called using the instance name

Static methods

Can only use static components in the implementation part

Can be called using the class name

Methods : Instance and Static


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PUBLIC SECTION.

ETHODS: set_name IMPORTING im name TYPE string.

CLASS-METHODS: get_count RETURNING VALUE(re_count) TYPE I.

PRIVATE SECTION.


CLASS-DATA: count TYPE I.

ENDCLASS.

CLASS lcl airplane IMPLEMENTATION.

...

METHOD get_count.

re_count = count.

ENDMETHOD

ENDCLASS.

Methods Instance and Static : Example

Gl b l t k


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ObjectsObjects

ClassesClasses


MethodsMethods





Gl b l t k


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lcl_airplane

name

weight

... CREATE OBJECT

name: LH Berlinweight: 30,000 kg

Objects can only be created and addressed usingreference variables

Creating Objects

Global network


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CLASS lcl_airplane DEFINITION.

PUBLIC SECTION.

...

PRIVATE SECTION.

...

ENDCLASS.

CLASS lcl_airplane IMPLEMENTATION.

...

ENDCLASS.

DATA: airplane1 TYPE REF TO cl_airplane,

airplane2 TYPE REF TO cl_airplane.

Main memory

airplane2

airplane1

Reference Variables

Global networkC ti Obj t S t


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DATA: airplane1 TYPE REF TO lcl_airplane,

airplane2 TYPE REF TO lcl_airplane.

CREATE OBJECT airplane1.

CREATE OBJECT airplane2.

CREATE OBJECT .

Main memory

airplane1

airplane2

name:

weight: 0

name:weight: 0

Creating Objects : Syntax

Global networkA i i R f


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...DATA: airplane1 TYPE REF TO lcl airplane,

airplane2 TYPE REF TO lcl airplane.

CREATE OBJECT airplane1.CREATE OBJECT airplane2.

airplane1 = airplane2.

Main memory

airplane1

airplane2

name:weight: 0

name:weight: 0

Assigning References

Global networkG b C ll t


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...

DATA: airplane1 TYPE REF TO lcl_airplane,

airplane2 TYPE REF TO lcl_airplane.

CREATE OBJECT airplane1 EXPORTING ... .

CREATE OBJECT airplane2 EXPORTING ... .

airplane1 = airplane2.

Main memory

airplane1

airplane2

name: LH B

weight: 30,000 kg

name: AA Bost

weight: 45,000 kg

Garbage Collector

Global networkP i i l O i 6


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ObjectsObjects

ClassesClasses


MethodsMethods





Global networkReferences : Comparison


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DATA: airplane1 TYPE REF TO lcl airplane,

airplane2 TYPE REF TO lcl airplane.

CREATE OBJECT airplane1 EXPORTING im name = LH Berlin ...

CREATE OBJECT airplane2 EXPORTING im name = LH Berlin ...

IF airplane1 = airplane2. not equal to

...

ENDIF.

Main memory

airplane1

airplane2

n: LH Berlin

w: 30,000 kg

n: LH Berlin

w: 30,000 kg

References : Comparison

Global networkBuffering References 1


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DATA: airplane TYPE REF TO cl_airplane,

airplane_table TYPE TABLE OF REF TO cl_airplane.

CREATE OBJECT airplane.

APPEND airplane TO airplane_table.


APPEND airplane TO airplane_table.

Main memory

airplane_table

airplane

Main memory

airplane_table

airplane

Buffering References -1

Global networkBuffering References 2


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LOOP AT TO airplane_table INTO airplane.

* work with the current instance

ENDLOOP.

Main memory

airplane_table

airplane1

2

Buffering References -2

Global networkObject Reference as Attributes


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lcl_airplane lcl_wings

orientat

name: LH Berlin

weight: 30,000 kg

left_wing:

right_wing:

orientat .: rightlength: 15 m

.: left

length: 15 m

Object Reference as Attributes

Global networkExternal Access to Public Attributes


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Instance attribute:

->

Class attribute:

=>


PUBLIC SECTION.

DATA: name TYPE string READ-ONLY.

CLASS-DATA: count TYPE I READ-ONLY.

...

ENDCLASS.

...

DATA: airplane1 TYPE REF TO lcl_airplane.

DATA: airplane_name TYPE STRING,

n_o_airplanes TYPE i.

...

airplane_name = airplane1->name.

n_o_airplanes = lcl_airplane=>count.

name: LH Berlin

External Access to Public Attributes

Global network

f i i Calling Methods


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O2

DataDo_itData Run

O1

call method O2->Do_it

Calling Methods

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Instance methods: CALL METHOD->

EXPORTING =

IMPORTING =

CHANGING =

RECEIVING =

EXCEPTIONS = .

Static methods: CALL METHOD=>

EXPORTING ... .

DATA: airplane TYPE REF TO lcl_airplane.


DATA: count_planes TYPE I.


CALL METHOD airplane->set_name EXPORTING im_name = name.

CALL METHOD lcl_airplane=>get_count RECEIVING re_count = count_planes.

Calling Methods : Syntax

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Constructor


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CREATE OBJECT

lcl_airplane

name

weight

count

constructor

ETHODS CONSTRUCTOR IMPORTINGEXCEPTIONS.ETHODS CONSTRUCTOR IMPORTINGEXCEPTIONS.

name: LH Berlin

weight: 30,000 kg

Special method for creatingobjects with defined initialstate

Only has IMPORTING

parameters andEXCEPTIONS

Exactly one constructor isdefined per class (explicitlyor implicitly)

Is executed exactly once perinstance

Constructor

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Constructor : Example


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PUBLIC SECTION.

METHODS CONSTRUCTOR IMPORTING im_name TYPE stringim_weight TYPE I.

PRIVATE SECTION.

DATA: name TYPE string, weight TYPE I.

CLASS-DATA count TYPE I.

ENDCLASS.

CLASS lcl_airplane IMPLEMENTATION.

METHOD CONSTRUCTOR.

name = im_name.weight = im_weight.

count = count + 1.

ENDMETHOD.

ENDCLASS.

DATA airplane TYPE REF TO lcl_airplane.

...

CREATE OBJECT airplaneEXPORTING im_name = `LH Berlin`

im_weight = 30000.

name: LH Berlin

weight: 30,000 kg

Constructor : Example

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Static Constructor


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CLASSlcl airplane DEFINITION.PUBLIC SECTION.CLASS-METHODS:CLASS_CONSTRUCTOR,get_count RETURNING

VALUE(re_count) TYPE I.CLASS-DATA: count TYPE I.

ENDCLASS.

CLASSlcl airplane IMPLEMENTATION.METHOD CLASS_CONSTRUCTOR.

...ENDMETHOD....

ENDCLASS.

CLASS DEFINITION.PUBLIC SECTION.CLASS-METHODSCLASS_CONSTRUCTOR.

ENDCLASS.

CLASS IMPLEMENTATION.ETHODCLASS_CONSTRUCTOR....

ENDMETHOD.ENDCLASS.

CLASS DEFINITION.PUBLIC SECTION.CLASS-METHODSCLASS_CONSTRUCTOR.

ENDCLASS.

CLASS IMPLEMENTATION.ETHODCLASS_CONSTRUCTOR....

ENDMETHOD.ENDCLASS.

Static Constructor

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* Example 1:

DATA airplane TYPE REF TOcl airplane.


* Example 2:

DATA class_id TYPE string.

class_id =lcl airplane=>count.

* Example 3:

DATA count_airplane TYPE I.

CALL METHODlcl airplane=>get_count

RECEIVING re_count = count_airplane.

Special static method

Automatically called

before the class is first

accessed

Only executed once per

program

Call To Static Constructor

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ObjectsObjects

ClassesClasses


MethodsMethods




p

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Class as capsule for functions

Defined responsibilities within a capsule (class)

Defined interfaces using

Public components of class (PUBLIC SECTION)

Interfaces

Implementation of component remains hidden through

limited visibility (PRIVATE SECTION)

p

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Server

DataDo_itDataRun

Client

CALL METHOD server->Do_it

Classes behave toward each other as client/serversystems.

Classes normally play both roles.

Responsibilities between the classes must be established.

Global network

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lcl _tank

fuel : i

fuel_max : i

get_fuel_level () : re_level

lcl _client

lcl _airplane

tank : lcl _tank

get_fuel_level () : re_level

re_level = fuel / fuel_max * 100.re_level = tank->get_fuel_level ( ).

g p

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Delegation : Sequence Diagram


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pilot : lcl _client airbus : lcl _airplane tank : lcl _tank

1: get_fuel_level ( )

2: get_fuel_level ( )

re_level

re_level

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The same namespace for

Attribute names

Method names

Event names

Type names

Constant names

ALIAS names

There is a local namespace within methods

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CLASS lcl airplane DEFINITION.PUBLIC SECTION.METHODS CONSTRUCTOR

IMPORTING im name TYPE stringimweight TYPE I.

PRIVATE SECTION.DATA name TYPE string.DATA weight TYPE I.

ENDCLASS.CLASS cl airplane IMPLEMENTATION.METHOD CONSTRUCTOR.

DATA name TYPE string VALUE `-airplane`.CONCATENATE im name name INTO E->name.

weight = imweight.ENDMETHOD.

ENDCLASS.

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Introduction to ABAP Objects1

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