Wood J. Object-Oriented Programming with ABAP Objects
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2 | Working with Objects
tions, Chapter 11, ABAP Object Services, and Chapter 9, Unit Testing with
ABAP Unit, respectively. The FINAL checkbox is related to inheritance, which is
covered in Chapter 5, Inheritance; for now, leave it de-selected.
4. Finally, the ONLY MODELED checkbox is used to exclude the class from the class
pool that gets saved to the ABAP Repository. This attribute can be used to make
sure that classes in the early stages of development (i.e., modeled classes) are
not used in the runtime environment. Such classes can be implemented later by
selecting CLASS • IMPLEMENT from the menu bar of the Class Editor.
5. When you click the SAVE button, you are prompted with the CREATE OBJECT
DIRECTORY ENTRY dialog box shown in Figure 2.9. Here, you can select the rel-
evant package name (or the local package $TMP) and click the SAVE button to
save the class.
After the class is saved, the new class is displayed in an inactive state in the
Class Editor screen (see Figure 2.15).
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Figure 2.15 Class Editor Screen
2.4.4 Defining Class Components
You can define the components of a global class in the Class Editor part of the
Class Builder as shown in Figure 2.15. The following subsections describe how to
create various types of components within the Class Editor.
74
Getting Started with the Class Builder
Attributes
Attributes are defined on the ATTRIBUTES tab of the Class Editor. This tab of the
Class Editor provides an entry table in which you can specify all of the various
attributes for a class (see Figure 2.16).
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Figure 2.16 Defining Attributes in the Class Editor
The name of an attribute is specified in the ATTRIBUTE column. The LEVEL column
is used to define the declaration type of the attribute. Figure 2.17 shows a list of
possible declaration types available in the input value help for this column. As
you can see. global class attributes can be declared as an INSTANCE ATTRIBUTE, a
STATIC ATTRIBUTE, or a CONSTANT.
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Figure 2.17 Setting the Declaration Type for an Attribute
The VISIBILITY column is used to define the visibility section assignment for an
attribute (for a list of possible values, see Figure 2.18).
The TYPING/ASSOCIATED TYPE columns are used to declare the data type for an
attribute. The TYPING field qualifies the type assigned to the attribute by specify-
ing the typing method (see Figure 2.19). These typing methods are described in
more detail in Table 2.3.
75
2 | Working with Objects
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Figure 2.19 Setting the Typing Method for an Attribute
Typing Method Description
LIKE Defines an attribute's type by referencing the type associated
with a class attribute from any globally defined class.
TYPE Defines an attribute's type using an A8AP native type or a glo-
bal type defined in the ABAP Dictionary.
TYPE REF TO Defines an attribute's type in reference to an object type (i.e.,
another global class) or a data type (i.e., a data reference).
Table 2.3 ABAP Objects Typing Methods
It is also possible to define an attribute's type directly by clicking on the DIRECT
TYPE ENTRY button in the column to the right of the ASSOCIATED TYPE column. This
button brings you to an ABAP Editor screen where you can specify the attribute
type in the same way that you learned how to define attributes for local classes in
Section 2.1.2, Declaring Components.
In the DESCRIPTION column, you can enter
a
basic descriptive text that describes
the purpose of the attribute. The INITIAL VALUE column can be used to define an
initial value for elementary attributes in a class.
76
Getting Started with the Class Builder 2.4
Methods
Methods are defined on the METHODS tab in the Class Editor. Here, much like you
saw on the ATTRIBUTES tab, the Class Editor provides you with an input table for
defining the methods of
a
class (see Figure 2.20).
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Figure 2.20 Defining Methods in the Class Editor
The method name is entered in the METHOD column. The LEVEL column allows
you to specify whether the method is an instance method or a static method (see
Figure 2.21). In the VISIBILITY column, you can determine which visibility section
that you want to assign the method to (refer to Figure 2.18 for a list of possible
visibility section options). You can also enter an optional descriptive text for the
method in the DESCRIPTION column.
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Figure 2.21 Setting the Declaration Type for a Method
After you have specified the basic attributes of the method, you can complete its
signature definition by declaring its parameter interface.
77
2 | Working with Objects
1. To define the parameters for a method, place your cursor on the name of the
method that you want to edit in the METHOD column.
2. Click on the PARAMETERS button in the toolbar above the method input table.
This will open up the METHOD PARAMETERS input screen for the selected method
(see Figure 2.22).
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Figure 2.22 Defining Method Parameters
3. In the METHOD PARAMETERS input table, you can specify the following:
The name of
a
parameter in the PARAMETER column; refer to Table 2.1 for a
list of naming conventions.
The TYPE column is used to specify whether the parameter is an importing,
exporting, changing, or returning parameter.
The PASS BY VALUE column contains a checkbox that indicates whether or
not the parameter should be passed by value or by reference.
The OPTIONAL column contains a checkbox that can be used to mark a
parameter as optional when the method is called. When selected, you can
optionally specify a default value for the parameter in the DEFAULT VALUE
column.
The TYPING METHOD/ASSOCIATED TYPE columns are used to define the type of
the parameter in the same way that attribute types are defined on the
ATTRIBUTES tab. You can also enter an optional descriptive text to describe
the parameter in the DESCRIPTION column.
4. After you have finished specifying the method parameters, you can click on the
METHODS button in the toolbar above the method parameters to return to the
normal method editor view.
5. To edit the method's implementation, you can either double-click on the
method name, or click on the SOURCE CODE button (see Figure 2.23).
78
Getting Started with the Class Builder
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Figure 2.23 Navigating to the Method Source Code Editor
6. In the source code editor, you can implement the method inside of a
METHOD... ENDMETHOO processing block within the ABAP Editor as per usual (see
Figure 2.24).
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Figure 2.24 Editing a Method Implementation in the ABAP Editor
Events
Events are defined on the EVENTS tab of the Class Editor. Here, you are provided
with an input table similar to the ones used to specify components on the
ATTRIBUTES and METHODS tabs (sec Figure 2.25).
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Figure 2.25 Defining Events in the Class Editor
79
2 | Working with Objects
1. In the event input table, you can enter the following:
The name of an event in the EVENT column.
The TYPE column is used to specify the declaration type of the event (i.e..
instance event versus static event).
In the VISIBILITY column, you can assign the event to a visibility section in
the class (refer to Figure 2.18 for a list of possible visibility section
options).
The optional DESCRIPTION field can be used to enter a descriptive text about
the event.
2. To declare the parameters for the event, place your cursor on the name of the
target event in the EVENT column, and click the PARAMETERS button in the tool-
bar above the input table. This opens up the EVENT PARAMETERS input screen
shown in Figure 2.26.
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Figure 2.26 Defining Event Parameters
3. Here, you can specify the exporting parameters of the event in much the same
way thatyou learned how to define method parameters in the previous section.
Types
Custom data types can be defined on the TYPES tab of the Class Editor. As you can
see in Figure 2.27, the TYPES tab provides an input table thatyou can use to spec-
ify the details of the custom types.
1. In the
TYPE
column, you can enter type names according to the naming conven-
tion TY_<type name>.
2. The VISIBILITY column is used to assign the custom type to a particular visibility
section with the class (refer to Figure 2.18 for a list of options).
3. The TYPING METHOD/ASSOCIATED TYPE fields arc used to define the type in the
same way that attribute types are defined on the ATTRIBUTES tab.
80
Getting Started with the Class Builder 2.4
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Figure 2.27 Defining Custom Types in the Class Editor
As was the case with attributes, it is also possible to specify custom types directly
using the DIRECT TYPE ENTRY button (see Figure 2.27). Clicking on this button takes
you to an ABAP Editor screen that allows you to edit the declaration part ofyour
class for the related visibility area (e.g.. PUBLIC SECTION, PRIVATE SECTION, etc.).
In Figure 2.28, type
TY_NAME
is declared as a structure containing three compo-
nents to represent the first name, middle initial, and last name, respectively.
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Figure 2.28 Defining Custom Types Using Direct Type Entry
Local types can also be defined outside of the class in the class pool. These types
are used to support the creation of local variables in method implementations,
and so on. To define these types, click on the LOCAL TYPES button in the top-level
toolbar of the Class Editor.
Local Inner Class Definitions
The Class Builder also allows you to create local helper classes inside the class
pool. These classes are useful for implementing internal details of the class and
81
2 | Working with Objects
should be used to simplify the interface of the global class by removing an over-
abundance of private helper methods.
You can edit local classes by clicking on the IMPLEMENTATION button in the top-
level toolbar of the Class Editor. This will take you to an ABAP Editor screen
where you can create local classes using the same local class definition syntax
described earlier in this chapter.
2.4.5 Editing the Class Definition Section Directly
As stated previously, the Class Builder tool quietly generates ABAP Objects class
definition syntax behind the scenes as you edit global classes. You can access the
definition sections of
a
global class by selecting the menu options GOTO • PUBLIC
SECTION, GOTO • PROTECTED SECTION, and GOTO • PRIVATE SECTION, respectively, in
the Class Builder menu bar. For example, if you look closely at the ABAP Editor
screenshot shown in Figure 2.28, you will notice that the custom type TV_NAME is
being edited directly in the
PRIVATE SECTION
of the global class definition.
2.5 Case Study: Working with Regular Expressions
The demonstrative classes that we have reviewed thus far have been extremely
straightforward and uncomplicated. However, one of the beauties of object-ori-
ented programming is the fact that you can encapsulate complex logic inside of a
class that can be used by programmers who may or may not understand how it
works.
SAP provides many useful global classes in the standard distribution that can be
used right out of the box. An example of this is the regular expression API pro-
vided in classes
CL_ABAP_REGEX
and
CL_ABAP_MATCHER.
A regular expression is a
text string that is used to describe a search pattern in text. A regular expression
consists of literal characters and metacharacters. You can think of metacharacters
as a type of shorthand for describing certain character patterns — similar to the
use of the asterisk for representing one or more characters in a search help lookup
(see Figure 2.29). However, regular expressions are much more powerful, provid-
ing a more generalized syntax that can be used to express many different types of
complex text patterns.
82
Case Study: Working with Regular Expressions
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Figure 2.29 Using Metacharacters in a Search Help Query
An example of
a
regular expression that could be used to match a telephone num-
ber in the (xxx)xxx-xxxx format is shown in Figure 2.30.
Parenthesis ParSXs, **
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\ (\ d {3} \) \ d { 3 } - \ d {4}
^T^ ^T^
Match Match Match
Three Three Four
Characters Characters Characters
in the in the in the
Range 0-9 Range 0-9 Range 0-9
Figure 2.30 Regular Expression for Matching Phone Numbers
The report program YREGEX_DEMO shown in Listing 2.24 shows how to use the
ABAP regular expression class libraiy to validate a phone number entered as a
parameter on a selection screen.
REPORT yregex_demo.
SELECTION-SCREEN BEGIN OF BLOCK blk_main.
PARAMETERS:
p_phone TYPE ad_tlnmbrl.
SELECTION-SCREEN ENO OF BLOCK blk_main.
AT SELECTION-SCREEN ON p_phone.
PERFORM check_phone_number.
83