Wood J. Object-Oriented Programming with ABAP Objects

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2 | Working with Objects

ABAP Expression Where Used

COMPUTE In the arithmetic expressions.

Example:

COMPUTE c- oref->get_a( ) +

oref->get_b( ).

C - oref->get_a( ) +oref->get_b( ).

Logical expressions

(e.g.. IF)

As an operand in a boolean expression.

Example:

IF oref->get_weight( ) GT 100.

ENDIF.

CASE/WHEN As the operand in a CASE or

WHEN

statement.

Example:

CASE oref->get_type( ).

WHEN oref >get_valuel( ).

ENDCASE.

LOOP AT/DELETE/MODIFY

In the WHERE clause.

Example:

LOOP AT itab

WHERE field EO oref->get_val( ).

ENOLOOP.

Table 2.2 Using Functional Methods in Expressions (cont.)

2.3 Building Your First Object-Oriented Program

In this section, we will create and test our first object-oriented program. In this

example, we will integrate a local class called lcl_date inside of an executable

program (i.e., a report program) named

YDATE_DEMO.

The lcl_date class encapsu-

lates the concept of

date, providing some utility methods for displaying the date

in various formats, and so on.

1. To create the test driver program, start up an SAP session, and open the Object

Navigator (Transaction SE80).

Building Your First Object-Oriented Program 2-3

2. In the object list selection of the Repositoiy Browser, select the PROGRAM

option, enter the name of the program (see Figure 2.5). and press L"*

"!.

•ftMiME Repository

frRepof

too Browser

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Figure 2.5 Creating a Test Driver Program

3. When prompted to create the new Repositoiy object, select the

YES

button (see

Figure 2.6).

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•

Program YDATE.DEMO ooes not «mt

Create Otxect?

Yes NO X Cancel |

N « •

Figure 2.6 Create Repository Object Confirmation Dialog Box

4. Next, in the CREATE PROGRAM dialog box (see Figure 2.7), you will be prompted

to determine whether or not you want to create a Top Include for your program.

Because we are only creating

simple report, you can de-select the WITH TOP

INCL. checkbox, and press Q-

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Figure 2.7 Create Program Dialog Box

5. In the ABAP PROGRAM ATTRIBUTES dialog box (see Figure 2.8), you can confirm

the various attributes for the program. Here, program type EXECUTABLE PRO-

2 | Working with Objects

GRAM has been selected. INCLUDE PROGRAM, MODULE POOL, and so on could

also have been selected — local classes can be defined in many different types

of programs. For now, accept the defaults, and click the SAVE button.

LE-ABAP Program MbiDules YDATE_DEMO CMnje • 1

Tfle Test Drwer Progr»m to Demonstrate lie Use of Local Classes

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Figure 2.8 ABAP Program Attributes Dialog Box

6. In the CREATE OBJECT DIRECTORY ENTRY dialog box (see Figure 2.9), you can spec-

ify a package that you want to create the program in, or you can select LOCAL

OBJECT to create the program in the temporary objects ($TMP) package. Objects

created in this package are never transported, so this is a good place to work on

examples.

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Building Your First Object-Oriented Program

7. Finally, you should be taken to an ABAP Editor screen where you can start cod-

ing. The source code for the example is given in Listing 2.22.

REPORT YDATEJJEMO.

CLASS lcl.date DEFINITION.

PUBLIC SECTION.

METHODS:

set_date IMPORTING im_month TYPE numc2

im_day TYPE numc2

im_year TYPE numcl.

as_native_date RETURNING value(re_date)

TYPE sydatum.

display_short_format RETURNING value(re_date)

TYPE string.

display_long_format RETURNING value(re_date)

TYPE string.

get_day_of_week RETURNING value(re_weekday)

TYPE string.

get_month_name RETURNING value(re_month)

TYPE string.

PRIVATE SECTION.

DATA: month TYPE numc2.

day TYPE numc2.

year TYPE numc4.

ENOCLASS.

CLASS lcl.date IMPLEMENTATION.

METHOD set_date.

month - im_month.

day - im_day.

year - im_year.

ENDMETHOD.

METHOD as_native_date.

CONCATENATE year month day INTO re_date.

ENDMETHOD.

"Month: 1-12

"Day: 1-31

"Year

METHOD display_short_format.

CONCATENATE month day year INTO re_date

SEPARATED BY '/'.

2 | Working with Objects

ENDMETHOD.

METHOD display_1ong_format.

Local Oata Declarations:

DATA: 1v_weekday TYPE string. "Week Day (String)

lv_month TYPE string. "Month Name

Determine the day of the week & the month name:

lv_weekday - get_day_of_week( ).

lv_month - get_month_name( ).

Format the date string in longhand format:

CONCATENATE 1v_weekday \

lv_month ' ' day ' year

INTO re.date

RESPECTING BLANKS.

ENDMETHOD.

METHOD get_day_of_week.

Local Data Declarations:

DATA: lv_date TYPE sydatum. "Date in Native Fmt.

lv_day TYPE p. "Day Integral Value

lt_day_names TYPE STANDARD TABLE

OF t?46. "Day Names

ls_day_name TYPE t246. "Day Name

Use the functionality of the ABAP native date type

"D" to determine the week day (as an integer):

lv_date - as_native_date( ).

1v_day - lv_date MOD 7.

IF 1v_day GT 1.

1v_day - lv_day - 1.

ELSE.

lv_day - lv_day + 6.

ENDIF.

Use the standard function module OAY_NAMES_GET to

determine the name of the derived day value:

CALL FUNCTION 'DAY_NAMES_GET'

TABLES

day_names - lt_day_names

EXCEPTIONS

Building Your First Object-Oriented Program

2-3

ddy_names_not_found - 1

OTHERS - 2.

READ TABLE lt_day_names INTO ls_day_name

WITH KEY wotnr - lv_day.

IF sy-subrc EQ 0.

re_weekday - 1s_day_name-langt.

ENDIF.

ENDMETHOD.

METHOD get_month_name.

Local Data Declarations:

OATA: 1t_month_names TYPE STANDARO TABLE

OF t247. "Month Names

1s_month_name TYPE t247. "Month Name

Determine the month name:

CALL FUNCTION 'M0NTH_NAMES_6ET'

TABLES

month_names - lt_month_names

EXCEPTIONS

month_names_not_found - 1

OTHERS - 2.

READ TABLE 1t_month_names INTO 1s_month_name

WITH KEY mnr - month.

IF sy-subrc EQ 0.

re_month - ls_month_name-ltx.

ENDIF.

ENDMETHOD.

ENOCLASS.

Global Data Declarations:

OATA: gr_date TYPE REF "Date Object Ref.

TO lcl_date.

gv_display TYPE string. "Date Display Value

START-OF-SELECT ION.

* Create an instance of class lcl_date:

CREATE OBJECT gr_date.

* Initialize the date to 9/13/2009:

2 | Working with Objects

CALL METHOD gr_date->set_date

EXPORTING

im_month - '9'

im_day - '13'

1m_year - '2009*.

* Display the date in shorthand format (e.g. mm/dd/yyyy):

gv_display - gr_date->display_short_format( ).

WRITE: / 'Date in shorthand format:'. gv_display.

* Display the date in longhand format:

gv_display - gr_date->display_long_format( ).

WRITE: / 'Date in longhand format:'. gv_display.

Listing 2.22 Program YDATE_DEMO

As you can see in Listing 2.22, program VDATE_OEMO creates an instance of class

lcl_date, initializes the date value, and displays the date in a couple of different

formats. The output of this program is shown in Figure 2.10.

Test Driver Program to Demonstrate the Use of Local Classes]

Tost Cri¥«r Progra* to Dwonttrat* tha U*a of local Clatsot

5ate in shorthand foraat 99/13/2009

>at« in longhand TorMt Sunday. S«9tMMr 13. 2009

Figure 2.10 Output of Example Program YDATE_DEMO

For demonstration purposes, the definition of class lcl_date is included inside

the main executable program shown in Listing 2.22. In a real-world scenario, you

would probably create an include program to define the local class just as you

would normally do for other type declarations. You should do this partly because

to avoid clutter in the main program, but the primary benefit comes from an

increased opportunity for reuse. Local classes are only visible in the context in

which they arc defined. Therefore, if you define a local class in an include pro-

gram, then that class can be included in other executable programs, module

pools, and so on. So, if you want to work with local classes in your programs, it

is highly recommended that you define them in a separate include program. Of

course, normally you should to define such classes as global Repositoiy objects.

You will see how to do that in the following section 2.4, Getting Started with the

Class Builder.

Getting Started with the Class Builder

2.4 Getting Started with the Class Builder

The Class Builder is a fully integrated development environment inside the ABAP

Workbench that can be used to edit global classes within the ABAP Repositoiy.

Most of the time, you will define your classes globally so that they can be reused

in other programs more easily. Therefore, it is important to get comfortable

working with the Class Builder because you will likely be spending a lot of time

there.

2.4.1 Class Pools

Global classes are stored within the ABAP Repositoiy inside of

class pool. A class

pool is a special ABAP program type that defines a single global Repository class

along with related local type definitions used to support the implementation of

the class. Class pools are similar to function groups in the sense that they cannot

be executed directly. Instead, runtime object instances are created in reference to

the global class type using the same CREATE OBJECT statement described in Section

2.2.2, Creating Objects.

2.4.2 Accessing the Class Builder

The Class Builder can be accessed via Transaction SE24, or using the menu path

TOOLS • ABAP WORKBENCH • DEVELOPMENT • SE24 - CLASS BUILDER, as shown in Fig-

ure 2.11.

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It is also possible to access the Class Builder from within the Object Navigator

(Transaction SE80). Here, you can select the CLASS/INTERFACE entry in the object

list selector drop-down list in the Repositoiy Browser, enter the name of the class

in the corresponding object type field, and click the DISPLAY button. This will load

2 | Working with Objects

the class inside an instance of the Class Builder that is embedded inside the con-

tent area of the Object Navigator (see Figure 2.12).

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2.4.3 Creating Classes

After starting the Class Builder via Transaction SE24, you will be presented with

the overview screen shown in Figure 2.13.

1. To create a new class in the ABAP Repository, enter the name of the class in the

OBJECT TYPE field. Class names can be up to 30 characters long and should be

named according to the convention shown in Listing 2.23.

(Y|Z|Namespace >CL_<class_name>

Listing 2.23 General Syntax for Defining Global Classes

Getting Started with the Class Builder 2.4

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Figure 2.13 Class Builder - Initial Screen

Because classcs arc meant to represent some kind of real-world phenomena,

the class_name portion of the naming convention should be made up of

singular nouns. For example, a purchase order class might be called

ZCL_PURCHASE_OROER.

2. After entering the class name, click on the CREATE button. Next, you will be

prompted with the CREATE CLASS dialog box shown in Figure 2.14. Here, you

can enter a short description of the class (DESCRIPTION), the instantiation type

(INSTANTIATION), and the class type (CLASS TYPE). We will discuss the instantia-

tion type in Chapter 4, Object Initialization and Cleanup; for now, accept the

default PUBLIC value.

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3. Accept the default value for class type (e.g.. USUAL ABAP CLASS) as well. The

remaining class types are described in Chapter 8, Error Handling with Excep-