Naked Global Reference
Following a subscripted global reference, InterSystems IRIS sets a naked indicator to that global name and subscript level. You can then make subsequent references to the same global and subscript level using a naked global reference, omitting the global name and higher level subscripts. This streamlines repeated references to the same global at the same (or lower) subscript level.
Specifying a lower subscript level in a naked reference resets the naked indicator to that subscript level. Therefore, when using naked global references, you are always working at the subscript level established by the most recent global reference.
The naked indicator value is recorded in the $ZREFERENCE special variable. The naked indicator is initialized to the null string. Attempting a naked global reference when the naked indicator is not set results in a <NAKED> error. Changing namespaces reinitializes the naked indicator. You can reinitialize the naked indicator by setting $ZREFERENCE to the null string ("").
In the following example, the subscripted global ^Produce(“fruit”,1) is specified in the first reference. InterSystems IRIS saves this global name and subscript in the naked indicator, so that the subsequent naked global references can omit the global name “Produce” and the higher subscript level “fruit”. When the ^(3,1) naked reference goes to a lower subscript level, this new subscript level becomes the assumption for any subsequent naked global references.
SET ^Produce("fruit",1)="Apples" /* Full global reference */
SET ^(2)="Oranges" /* Naked global references */
SET ^(3)="Pears" /* assume subscript level 2 */
SET ^(3,1)="Bartlett pears" /* Go to subscript level 3 */
SET ^(2)="Anjou pears" /* Assume subscript level 3 */
WRITE "latest global reference is: ",$ZREFERENCE,!
ZWRITE ^Produce
KILL ^Produce
This example sets the following global variables: ^Produce("fruit",1), ^Produce("fruit",2), ^Produce("fruit",3), ^Produce("fruit",3,1), and ^Produce("fruit",3,2).
With few exceptions, every global reference (full or naked) sets the naked indicator. The $ZREFERENCE special variable contains the full global name and subscripts of the most recent global reference, even if this was a naked global reference. The ZWRITE command also displays the full global name and subscripts of each global, whether or not it was set using a naked reference.
Naked global references should be used with caution, because InterSystems IRIS sets the naked indicator in situations that are not always obvious, including the following:
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A full global reference initially sets the naked indicator, and subsequent full global references or naked global references change the naked indicator, even when the global reference is not successful. For example attempting to WRITE the value of a nonexistent global sets the naked indicator.
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A command postconditional that references a subscripted global sets the naked indicator, regardless of how InterSystems IRIS evaluates the postconditional.
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An optional function argument that references a subscripted global may or may not set the naked indicator, depending on whether InterSystems IRIS evaluates all arguments. For example the second argument of $GET always sets the naked indicator, even when the default value it contains is not used. InterSystems IRIS evaluates arguments in left-to-right sequence, so the last argument may reset the naked indicator set by the first argument.
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The TROLLBACK command, which rolls back a transaction, does not roll back the naked indicator to its value at the beginning of the transaction.
If a full global reference contains an extended global reference, subsequent naked global references assume the same extended global reference; you do not have to specify the extended reference as part of a naked global reference.
