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Validity and Visibility

The context of a declarative statement in the source code of a program determines the validity and visibility of the declared comporent. In ABAP programs, there are three contexts in which data types and data objects can be declared:

All contexts see the program-independent type definitions of ABAP Dictionary and the type definitions and data declarations in the public visibility areas of global classes. Local declarations, however, hide global declarations with the same name. In statements, in which a dynamic specification of a data type, a class or an interface is possible, the hiding of a global type by a local type can be cancelled by specifying an absolute type name.

In addition to context-dependent visibility, the position of the declaration in the source text also plays a role. In a statement of an ABAP program only previous declarations are visible, regardless of the context. To enable the order in the program to match the context-dependent visibility, all global declarations of a program should be specified at the start of the source code, before the first processing block, and all local declarations should be specified directly after the introduction of a procedure. Viewed like this, the definition of an interface and the declaration part of a class are both global declarations. Remember that reference variables that reference a class cannot be declared until after the class has been declared. The implementation part, on the other hand, is one of the processing blocks.

Note

All data declared in the declaration part of an ABAP program is global to the program. With the exception of the event blocks AT SELECTION-SCREEN, all data declared within event blocks and dialog modules is global to the program. The data declared in the above event blocks is local to these event blocks. Data that is declared between discrete processing blocks is also global for the program.