Complete C_ABAPD_2309 SAP Materials

The predicate condition that can be used to ensure that the CAST will work is IS INSTANCE OF. The IS INSTANCE OF predicate condition checks whether the operand is an instance of the specified class or interface. This is useful when you want to perform a downcast, which is a conversion from a more general type to a more specific type. A downcast can fail if the operand is not an instance of the target type, and this can cause a runtime error. Therefore, you can use the IS INSTANCE OF predicate condition to check whether the downcast is possible before using the CAST operator12. For example:

The following code snippet uses the IS INSTANCE OF predicate condition to check whether the variable g_super is an instance of the class lcl_super. If it is, the CAST will work and the variable g_sub1 will be assigned the value of g_super.

DATA: g_super TYPE REF TO lcl_super, g_sub1 TYPE REF TO lcl_sub1. IF g_super IS INSTANCE OF lcl_super. g_sub1 = CAST #( g_super ). g_sub1->method( … ). ENDIF.

You cannot do any of the following:

IS SUPPLIED: The IS SUPPLIED predicate condition checks whether an optional parameter of a method or a function module has been supplied by the caller. This is useful when you want to handle different cases depending on whether the parameter has a value or not. However, this predicate condition has nothing to do with the CAST operator or the type of the operand12.

IS NOT INITIAL: The IS NOT INITIAL predicate condition checks whether the operand has a non-initial value. This is useful when you want to check whether the operand has been assigned a value or not. However, this predicate condition does not guarantee that the CAST will work, because the operand may have a value but not be an instance of the target type12.

IS BOUND: The IS BOUND predicate condition checks whether the operand is a bound reference variable. This is useful when you want to check whether the operand points to an existing object or not. However, this predicate condition does not guarantee that the CAST will work, because the operand may point to an object but not be an instance of the target type12.

References: 1: Predicate Expressions - ABAP Keyword Documentation - SAP Online Help 2: ABAP - Predicates | SAP Community

A projection view is a RESTful Application Programming object that contains only the fields required for a particular app. A projection view is a CDS view entity that defines a projection on an existing CDS view entity or CDS DDIC-based view. A projection view exposes a subset of the elements of the projected entity, which are relevant for a specific business service. A projection view can also define aliases, virtual elements, and annotations for the projected elements. A projection view is the top-most layer of a CDS data model and prepares data for a particular use case. A projection view can have different provider contracts depending on the type of service it supports, such as transactional query, analytical query, or transactional interface.

A database view is a CDS DDIC-based view that defines a join or union of database tables. A database view has an SQL view attached and can be accessed by Open SQL or native SQL. A database view can be used as a projected entity for a projection view, but it does not contain only the fields required for a particular app.

A metadata extension is a RESTful Application Programming object that defines additional annotations for a CDS view entity or a projection view. A metadata extension can be used to enhance the metadata of a CDS data model without changing the original definition. A metadata extension does not contain any fields, but only annotations.

A data model view is a CDS view entity that defines a data model based on database tables or other CDS view entities. A data model view can have associations, aggregations, filters, parameters, and annotations. A data model view can be used as a projected entity for a projection view, but it does not contain only the fields required for a particular app.

References: CDS Projection Views - ABAP Keyword Documentation, CDS Projection Views in ABAP CDS: What’s Your Flavor, Business Object Projection - ABAP Keyword Documentation

On-stack developer extensibility is a type of extensibility that allows you to create development projects directly on the SAP S/4HANA Cloud technology stack. It gives you the opportunity to develop cloud-ready and upgrade-stable custom ABAP applications and services inside the SAP S/4HANA Cloud, public edition system. You can use the ABAP Development Tools in Eclipse to create and deploy your on-stack extensions. On-stack developer extensibility is suitable for the following kinds of applications:

Applications that provide APIs for side by side SAP BTP apps. On-stack developer extensibility allows you to create OData services or RESTful APIs based on CDS view entities or projection views. These services or APIs can expose SAP S/4HANA data and logic to other applications that run on the SAP Business Technology Platform (SAP BTP) or other platforms. This way, you can create a loosely coupled integration between your SAP S/4HANA system and your side by side SAP BTP apps.

Applications that access SAP S/4HANA data using complex SQL. On-stack developer extensibility allows you to use ABAP SQL to access SAP S/4HANA data using complex queries, such as joins, aggregations, filters, parameters, and code pushdown techniques. You can also use ABAP SQL to perform data manipulation operations, such as insert, update, delete, and upsert. This way, you can create applications that require advanced data processing and analysis on SAP S/4HANA data.

The other kinds of applications are not suitable for on-stack developer extensibility, as they have different requirements and challenges. These kinds of applications are:

Applications that integrate data from several different systems. On-stack developer extensibility is not meant for creating applications that integrate data from multiple sources, such as other SAP systems, third-party systems, or cloud services. This is because on-stack developer extensibility does not support remote access or data replication, and it may cause performance or security issues. For this kind of applications, you should use side by side extensibility, which allows you to create applications that run on the SAP BTP and communicate with the SAP S/4HANA system via public APIs or events.

Applications that run separate from SAP S/4HANA. On-stack developer extensibility is not meant for creating applications that run independently from the SAP S/4HANA system, such as standalone apps, microservices, or web apps. This is because on-stack developer extensibility requires a tight coupling with the SAP S/4HANA system, and it may limit the scalability, flexibility, and portability of the applications. For this kind of applications, you should use side by side extensibility, which allows you to create applications that run on the SAP BTP and leverage the cloud-native features and services of the platform.

References: Developer Extensibility in SAP S/4HANA Cloud ABAP Environment, SAP S/4HANA Extensibility – Simplified Guide for Beginners