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ABAPINTERFACES_CLASS - INTERFACES CLASS

ABAPINTERFACES_CLASS - INTERFACES CLASS

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INTERFACES, implementation

Short Reference



INTERFACES intf
  $[PARTIALLY IMPLEMENTED$]
  ${ ${$[ABSTRACT METHODS meth1 meth2 ... $]
     $[FINAL METHODS meth1 meth2 ... $]$}
  $| $[ALL METHODS ${ABSTRACT$|FINAL$}$] $}
  $[DATA VALUES attr1 = val1 attr2 = val2 ...$].

Additions

1. ... ABSTRACT METHODS meth1 meth2 ...

2. ... FINAL METHODS meth1 meth2 ...

3. ... ALL METHODS ${ABSTRACT$|FINAL$}

4. ... DATA VALUES attr1 = val1 attr2 = val2 ...

Effect

In the public visibility section of a class, the statement INTERFACES implements the interface intf in the class. Additions can also be specified to determine the properties of interface components in the class.

All local or global interfaces that are visible here can be specified for intf that are not already included in a superclass of the current class. The components of the interfaces become public components of the class after the implementation. An interface component called comp has the name intf~comp in the class, where intf is the name of the interface and the character ~ is the interface component selector. A class must implement all methods of the interface in its implementation part, with the following exceptions:

  • Interface methods declared as optional using the addition DEFAULT.
  • Interface methods that are specified in the class after the addition ABSTRACT METHODS and are therefore declared as abstract.

Notes

  • A class can implement any number of different interfaces. All of the interfaces implemented by a class are equal and on the same level. If an interface intf implemented in a class is a composite, that is, it contains component interfaces, these are implemented in the class like individual interfaces, regardless of their nesting hierarchy, and their components are addressed using the name of their component interface instead of using the name intf. It is generally not possible to use the interface component selector multiple times in a name (intf1~intf2~comp).
  • Each interface appears only once in a class and every interface component comp is always clearly accessible using the intf~comp. Even the components of an interface that is the interface component of one or more other interface, and appears to be implemented multiple times in a class, only exist once.
  • If the implementation of a non-optional method of a global interface implemented using INTERFACES is missing in a class, a syntax warning occurs instead of a syntax error. This prevents classes from becoming unusable due to subsequent enhancements of global interfaces. Calling a missing implementation, however, always raises an exception of the class CX_SY_DYN_CALL_ILLEGAL_METHOD and, if not handled, produces the runtime error CALL_METHOD_NOT_IMPLEMENTED. A real syntax error is produced when local interfaces are used, and the implementation is missing.
  • If a class implements a method intf~... of a global interface intf implemented using INTERFACES in its implementation part and the method is not declared in the interface, a warning is raised by the syntax check. This type of method implementation is dead code that cannot be executed and should removed. Classes become unusable in the case of a syntax error if methods were later deleted from an implemented global interface, and which were implemented without a role in a class and had no values. An actual syntax error occurs when local interfaces are used.

Example

Implementation of an interface intf in a class cls.

Addition 1

... ABSTRACT METHODS meth1 meth2 ...

Addition 2

... FINAL METHODS meth1 meth2 ...

Effect

Using the additions ABSTRACT METHODS and FINAL METHODS, the individual instance methods meth of the interface can be made either abstract or final in the class to be implemented. The same rules apply as to the additions ABSTRACT and FINAL of the statement METHODS. In particular, the whole class must be abstract if an interface method is made abstract and no interface method can be listed after ABSTRACT METHODS and FINAL METHODS.

The following can be specified as methods meth1, meth2, ...

  • Instance methods that are declared in the interface intf itself.
  • Alias names declared in the interface intf for instance methods declared in interfaces that are included in intf.
  • Instance methods that are declared in interfaces included in intf using the name of their interface and the interface component selector (~). In this case the component interface cannot itself be included with the statement INTERFACES.

If an interface is included using multiple INTERFACES statements, the specifications in the additions FINAL and ABSTRACT must not produce contradictory definitions for a method.

Definition of abstract methods when including two interfaces intf1 and intf2 in an abstract class cls.

Short form of the preceding example. Since intf2 includes the interface intf1, its methods can be specified as intf1~meth1. This means that a separate statement INTERFACES intf1 is no longer possible in this class.

Addition 3

... ALL METHODS ${ABSTRACT$|FINAL$}

Effect

Instead of making individual interface methods in the class abstract or final it is possible, using the addition ALL METHODS ${ABSTRACT$|FINAL$}, to make all interface methods either abstract or final.

Implementation of an interface intf in an abstract class cls1, in which all methods are made abstract and must be implemented in a subclass cls2.

Addition 4

... DATA VALUES attr1 = val1 attr2 = val2 ...

Effect

Using the addition DATA VALUES, initial values can be assigned to individual attributes attr. For attributes, this addition fulfills the same functions as the addition VALUE of the statement DATA for attributes in its own class.

The following can be specified as attributes attr1, attr2, ...

  • Attributes that are declared in the interface intf itself.
  • Alias names declared in the interface intf for attributes declared in interfaces that are included in intf.
  • Attributes that are declared in interfaces included in intf using the name of its own interface and the interface component selector (~). In this case the component interface cannot itself be included with the statement INTERFACES.

Constants declared in the interface or in a component interface with the statement CONSTANTS cannot be specified after the addition DATA VALUES.

Example

Implementation of an interface intf in a class cls, where the interface attributes are assigned start values.






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