{name*O}, {name*N}, and {name*C} Trigger Code Syntax
Three ObjectScript syntax shortcuts are available in UPDATE trigger code.
You can reference the old (pre-update) value using the following syntax:
{fieldname*O}
where fieldname is the name of the field and the character after the asterisk is the letter “O” (for Old). For an INSERT trigger, {fieldname*O} is always the empty string ("").
You can reference the new (post-update) value using the following syntax:
{fieldname*N}
where fieldname is the name of the field and the character after the asterisk is the letter “N” (for New). This {fieldname*N} syntax can be used only to reference a value to be stored; it cannot be used to change the value. You cannot set {fieldname*N} in trigger code. Computing the value of a field on INSERT or UPDATE should be achieved by other means, such as SqlComputeOnChange.
You can test whether a field value has been changed (updated) using the following syntax:
{fieldname*C}
where fieldname is the name of the field and the character after the asterisk is the letter “C” (for Changed). {fieldname*C} evaluates to 1 if the field has been changed and 0 if it has not been changed. For an INSERT trigger, InterSystems IRIS sets {fieldname*C} to 1.
For a class with stream properties, an SQL trigger reference to the stream property {Stream*N} and {Stream*O} returns the OID for the stream, if the SQL statement (INSERT or UPDATE) did not insert/update the stream property itself. However, if the SQL statement did insert/update the stream property, {Stream*O} remains the OID, but the {Stream*N} value is set to one of the following:
-
BEFORE trigger returns the value of the stream field in whatever format it was passed to the UPDATE or INSERT. This could be the literal data value that was entered into the stream property, or the OREF or OID of a temporary stream object.
-
AFTER trigger returns the Id of the stream as the {Stream*N} value. This is the Id value InterSystems IRIS stored in the ^classnameD global for the stream field. This value is in the appropriate Id format based on the CLASSNAME type parameter for the stream property.
If a stream property is updated using InterSystems IRIS objects, the {Stream*N} value is always an OID.
Note:
For a trigger for child-tables created by an array collection of serial objects, trigger logic works with object access/save but does not work with SQL access (INSERT or UPDATE).
