The IFDEF macro allows you to define two possible outcomes based on whether or not a specified tag exists within a project at the time of compiling. The macro can be implemented anywhere a simple expression is used, including fields within relevant CitectSCADA dialogs.
The macro was primarily created to avoid the "Tag not found" compile error being generated whenever a genie was missing an associated tag. By allowing a "0" or "1" to be generated within the Hidden When field of a Genie's properties, elements could simply be hidden if a required tag was missing, allowing the genie to still be pasted onto a graphics page.
The macro accepts three arguments: the first specifies the tag that requires confirmation, the second defines the outcome if the tag exists, the third defines the outcome if it does not exist. In the case of a genie being pasted on a graphics page, the IFDEF function would be configured as follows in the Hidden When field of the object properties dialog:
If the tag "Bit_1" is defined in the tag database, the value in the Hidden When field will be 0. If Bit_1 is undefined, the value will be 1. Since the object is hidden when the value is TRUE (1), the object will be hidden when Bit_1 is undefined. See Hiding Graphics Objects for details.
Beyond this purpose, the IFDEF macro can be broadly used as a conditional variable. The [<value if defined>] and <value if not defined> arguments can support any variable, expression, or constant. The [<value if defined>] argument is optional; if you leave it blank it will generate the current variable. You can also use nested IFDEF macros.
Note: As different types of alarms can share the same name, you have to use a variation of IFDEF to check for the existence of alarm tags. See IFDEFAnaAlm for analog alarms, IFDEFDigAlm for digital alarms, or IFDEFAdvAlm for advanced alarms.
[<value if defined>]
<value if not defined>
If the tag specified in the first argument exists, the value defined by the second argument is returned. This could be a variable, expression, or constant, or the current tag value if the argument has been left blank. If the specified tag does not exist, the variable, expression, or constant defined by the third argument is returned.
! Generate the tag value if tag "Bit_1" is defined
! Generate an empty string if "Bit_1" is not defined
! Generate a zero value (0) if tag "Bit_1" is defined
! Generate a true value (1) if "Bit_1" is not defined
For more examples of how to implement the IFDEF macro, see the CitectSCADA Knowledge Base article Q3461.
IFDEFAnaAlm, IFDEFDigAlm, IFDEFAdvAlm, Hiding Graphics Objects, IFDEF macro