Preserve Run-Time Class
- Updated2023-02-17
- 4 minute(s) read
Preserve Run-Time Class
Typecasts a class object to a class you specify if both are in the same inheritance hierarchy.
target object
Class object whose class you want object in to match.
object in
Class object whose class you want to typecast to that of target object.
error in
Error conditions that occur before this node runs.
The node responds to this input according to standard error behavior.
Standard Error Behavior
Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.
| error in does not contain an error | error in contains an error |
|---|---|
| If no error occurred before the node runs, the node begins execution normally.
If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out. | If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out. |
Default: No error
object out
Class object of the same class as target object.
error out
Error information.
The node produces this output according to standard error behavior.
Standard Error Behavior
Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.
| error in does not contain an error | error in contains an error |
|---|---|
| If no error occurred before the node runs, the node begins execution normally.
If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out. | If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out. |
Automatic Typecasting Behavior
If you wire a child class to a subVI that accepts and returns a parent class in the inheritance hierarchy, the subVI automatically typecasts the class output to the same child class as the input. However, the class output is not automatically typecast if the subVI cannot verify that the class data type of a wire does not change across the diagram. When the class data type of a wire does not change across the diagram of a subVI, use Preserve Run-Time Class to typecast the class output immediately before returning it from the subVI.