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04_ABAP_Object_Orientation.md
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@@ -14,6 +14,8 @@
- [Class Attributes](#class-attributes)
- [Methods](#methods)
- [Parameter Interface](#parameter-interface)
- [Formal and Actual Parameters](#formal-and-actual-parameters)
- [Defingin Parameters as Optional](#defingin-parameters-as-optional)
- [Constructors](#constructors)
- [Example for Method Definitions](#example-for-method-definitions)
- [Working with Objects and Components](#working-with-objects-and-components)
@@ -508,6 +510,8 @@ ENDCLASS.
You declare them using `METHODS` statements in a visibility
section. Note that you must create an instance of a class first before using instance methods.
<p align="right"><a href="#top">⬆️ back to top</a></p>
#### Parameter Interface
In the simplest form, methods can have no parameter at all. Apart from that, methods can be defined with the following parameters:
@@ -524,46 +528,35 @@ In the simplest form, methods can have no parameter at all. Apart from that, met
> **💡 Note**<br>
> - Find more information [here](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abapmethods_general.htm).
> - You may find the addition `EXCEPTIONS` especially in definitions of older classes. They are for non-class-based exceptions. This addition should not be used in ABAP for Cloud Development.
> - Notes on [formal
parameter](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenformal_parameter_glosry.htm "Glossary Entry")
versus [actual
parameters](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenactual_parameter_glosry.htm "Glossary Entry"):
> - You define method parameters by specifying a name with a type which
can be a
[generic](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abengeneric_data_type_glosry.htm "Glossary Entry")
or
[complete](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abencomplete_data_type_glosry.htm "Glossary Entry")
type. Examples:
> - `fp` is the formal parameter that has a complete type: `... meth IMPORTING fp TYPE string ...`
> - `gen` is the formal parameter that has a generic type: `... meth IMPORTING gen TYPE any ...`
> - Find more information about generic types also in the [Data Types and Data Objects](16_Data_Types_and_Objects.md#generic-types) cheat sheet.
> - This formal parameter includes the specification of how the
value passing should happen. Parameters can be [passed by
reference](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenpass_by_reference_glosry.htm "Glossary Entry")
(`... REFERENCE(param) ...`; note that just specifying the
parameter name `... param ...` - as a shorter syntax -
means passing by reference by default) or [by
value](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenpass_by_value_glosry.htm "Glossary Entry")
(`... VALUE(param) ...`).
> - The actual parameter represents
the data object whose content is passed to or copied from a formal
parameter as an argument when a procedure is called. If
passing by reference is used, a local data object is not created for
the actual parameter. Instead, the procedure is given a
[reference](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenreference_glosry.htm "Glossary Entry")
to the actual parameter during the call and works with the actual
parameter itself. Note that parameters that are input and passed by
reference cannot be modified in the procedure. However, the use of a
reference is beneficial regarding the performance compared to
creating a local data object.
>- Parameters can be defined as optional using the
[`OPTIONAL`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abapmethods_parameters.htm#!ABAP_ONE_ADD@1@)
addition. In doing so, it is not mandatory to pass an actual
parameter. The
[`DEFAULT`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abapmethods_parameters.htm#!ABAP_ONE_ADD@1@)
addition also makes the passing of an actual parameter optional.
However, when using this addition, as the name implies, a default
value is set.
<p align="right"><a href="#top">⬆️ back to top</a></p>
#### Formal and Actual Parameters
- [Formal parameter](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenformal_parameter_glosry.htm "Glossary Entry")
versus [actual parameters](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenactual_parameter_glosry.htm "Glossary Entry"):
- [Formal parameters](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenformal_parameter_glosry.htm "Glossary Entry"): You define method parameters by specifying a name with a type which can be a [generic](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abengeneric_data_type_glosry.htm "Glossary Entry") or [complete](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abencomplete_data_type_glosry.htm "Glossary Entry")
type.
- Examples:
- `fp` is the formal parameter that has a complete type: `... meth IMPORTING fp TYPE string ...`
- `gen` is the formal parameter that has a generic type: `... meth IMPORTING gen TYPE any ...`
- Find more information about generic types also in the [Data Types and Data Objects](16_Data_Types_and_Objects.md#generic-types) cheat sheet.
- This formal parameter includes the specification of how the value passing should happen. Parameters can be passed by ...
- [reference](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenpass_by_reference_glosry.htm "Glossary Entry"): `... REFERENCE(param) ...`; note that just specifying the parameter name `... param ...` - as a shorter syntax - means passing by reference by default)
- [value](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenpass_by_value_glosry.htm "Glossary Entry"): `... VALUE(param) ...`
- The [actual parameters](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenactual_parameter_glosry.htm "Glossary Entry") represents the data object whose content is passed to or copied from a formal parameter as an argument when a procedure is called.
- If passing by reference is used, a local data object is not created for the actual parameter. Instead, the procedure is given a [reference](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenreference_glosry.htm "Glossary Entry") to the actual parameter during the call and works with the actual parameter itself.
- Note that parameters that are input and passed by reference cannot be modified in the procedure. However, the use of a reference is beneficial regarding the performance compared to creating a local data object.
<p align="right"><a href="#top">⬆️ back to top</a></p>
#### Defingin Parameters as Optional
- Parameters can be defined as optional using the `OPTIONAL` and `DEFAULT` additions:
- [`OPTIONAL`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abapmethods_parameters.htm#!ABAP_ONE_ADD@1@): It is then not mandatory to pass an actual
parameter.
- [`DEFAULT`](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abapmethods_parameters.htm#!ABAP_ONE_ADD@1@): Also makes the passing of an actual parameter optional. However, when using this addition, as the name implies, a default value is set.
- In the method implementations you may want to check whether an actual parameter was passed. You can use predicate expressions using `IS SUPPLIED`. See the example further down.
<p align="right"><a href="#top">⬆️ back to top</a></p>
@@ -711,6 +704,9 @@ ref1 = NEW #( ). "Type derived from already declared ref1
DATA(ref2) = NEW some_class( ). "Reference variable declared inline, explicit type
"(class) specification
"The assumption is that this class has no mandatory importing parameters for the
"instance constructor. If a class has, actual parameters must be provided.
DATA(ref_mand_param) = NEW another_class( ip1 = ... ip2 = ... ).
"Older syntax
"CREATE OBJECT ref3. "Type derived from already declared ref3
@@ -724,11 +720,9 @@ Some examples for working with reference variables:
**Assigning Reference Variables**
To assign or copy
reference variables, use the [assignment
To assign or copy reference variables, use the [assignment
operator](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenassignment_operator_glosry.htm "Glossary Entry")
`=`. In the example below, both object reference variables have the same
type.
`=`. In the example below, both object reference variables have the same type. Note the concepts of polymorphism, upcasts and downcasts when assigning reference variables covered further down.
``` abap
DATA: ref1 TYPE REF TO some_class,
@@ -1677,7 +1671,7 @@ ENDCLASS.
The table below includes selected syntax related to inheritance in class and method declarations.
> **💡 Note**<br>
> - Some of the syntax options have already been mentioned previously.
> - Some of the syntax options have already been mentioned previously. This is to summarize.
> - Here, the emphasis is on global classes.
> - The snippets provided do not represent all possible syntax combinations. For the complete picture, refer to the ABAP Keyword Documentation. Additional syntax options are available in the context of friendship (`GLOBAL FRIENDS/FRIENDS`), testing (`FOR TESTING`), [RAP](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenarap_glosry.htm) (`FOR BEHAVIOR OF`; to declare [ABAP behavior pools](https://help.sap.com/doc/abapdocu_cp_index_htm/CLOUD/en-US/index.htm?file=abenbehavior_pool_glosry.htm)), and more.
> - The order of the additions can vary.