Owning Palette: Variant Functions
Requires: Base Development System
Converts variant data to a LabVIEW data type so LabVIEW can display or process the data. You also can use this function to convert variant data to ActiveX data.
|type is the LabVIEW data type to which you want to convert the variant data. type can be any data type. However, this function returns an error if LabVIEW cannot convert the data wired to variant to the data type you wire to this input. If the data is integers, you can coerce the data to another numeric representation, such as an extended-precision, floating-point number.|
|variant is the variant data you want to convert to the LabVIEW data type specified in type.|
|error in describes error conditions that occur before this node runs. This input provides standard error in functionality.|
|data is the variant changed to the data type specified by type. If variant could not be converted to the data type specified, this data returns the default value for the data type.|
|error out contains error information. This output provides standard error out functionality.|
This function also serves the same purpose as the QueryInterface method of ActiveX. To use the Variant to Data function to switch between interfaces of an ActiveX object, first convert the automation refnum for the ActiveX object to a variant by using the To Variant function. Wire the variant version of the refnum to the variant input of the Variant to Data function. Then create another automation refnum and select the desired interface as the ActiveX class for the refnum. Wire this new automation refnum to the type input of the Variant to Data function. LabVIEW associates the specified interface with the automation refnum returned by data.
If you use the To Variant and Variant to Data functions with LabVIEW classes, note that variants do not recognize inheritance hierarchies. For example, if you have child data traveling on a parent class wire and you then wire the parent wire to a To Variant function, the variant recognizes only the parent data type. If you wire a child data type to the Variant to Data function to extract the child data, LabVIEW returns an error. You must wire the parent to the Variant to Data function. Then use the To More Specific function to retrieve the child class data.