5.3.16.5 "COBOL Language Reference" IBM Library Server

X 5.3.16.5 OBJECT REFERENCE Phrase

X A data item defined with the OBJECT REFERENCE phrase is an object
X reference.

X class-name-1

X An optional class name.

X You must declare class-name-1 in the REPOSITORY paragraph in the
X Configuration Section of the containing class or outermost program.
X If specified, class-name-1 indicates that data-name always refers to
X an object-instance of class class-name-1 or a class derived from
X class-name-1.

X If class-name-1 is not specified, data-name can refer to an object of
X any class. In this case, data-name-1 is a "universal" object
X reference.

X You can specify data-name-1 within a group item without affecting the
X semantics of the group item. There is no conversion of values or
X other special handling of the object references when statements are
X executed that operate on the group. The group continues to behave as
X an alphanumeric data item.

X METACLASS

X Indicates that the data-name always refers to a class object reference
X that is an instance of the metaclass of class-name-1 or of a metaclass
X derived from the metaclass of class-name-1.

X You can use these object references to INVOKE methods that are defined
X in the metaclass.

X The USAGE IS OBJECT REFERENCE clause can be used at any level except level
X 66 or 88. If a group item is described with the USAGE IS OBJECT REFERENCE
X clause, the elementary items within the group are object-reference data
X items. The group itself is not an object reference. The USAGE clause of
X an elementary item cannot contradict the USAGE clause of a group that
X contains the item.

X An object reference can be defined in any section of the data division of
X a class, method, or program, although it does not belong to any class or
X category. An object-reference data item can be used in only:

X A SET statement (Format 7 only)
X A relation condition
X An INVOKE statement
X The USING or RETURNING phrase of an INVOKE statement
X The USING or RETURNING phrase of a CALL statement
X A program Procedure Division or ENTRY statement USING or RETURNING
X phrase
X A method Procedure Division USING or RETURNING phrase

X Object reference data items:

X Are ignored in CORRESPONDING operations
X Are unaffected by INITIALIZE statements
X Can be the subject or object of a REDEFINES clause
X Cannot be a conditional variable
X Can be written to a file (but upon subsequent reading of the record
X the content of the object reference is undefined)

X A VALUE clause for an object-reference data item can contain only NULL or
X NULLS.

X You can use the SYNCHRONIZED clause with USAGE IS OBJECT REFERENCE to
X obtain efficient alignment of the object-reference data item.

X The DATE FORMAT, JUSTIFIED, PICTURE, and BLANK WHEN ZERO clauses cannot be
X used to describe group or elementary items defined with the USAGE IS
X OBJECT REFERENCE clause.

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X 5.3.16.5 OBJECT REFERENCE Phrase

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