Table Of Contents

Register For Events (G Dataflow)

Last Modified: January 12, 2018

Registers events for use with an Event Structure. The events that you can register depend on the type of the reference you wire to each event source input.

Programming Patterns
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event registration refnum

Reference to an existing event registration that a Register For Events node created.

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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

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event source 1..n

Reference to a user event or device event, such as a DAQ event. The reference you wire to this input must be to a local object. You cannot wire a reference to an object on a remote computer or other hardware.

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event registration refnum

Reference to the new or modified event registration. Wire this output to another Event node that accepts event registration refnums, such as an Event Structure or Register For Events node.

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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.

Dynamic Event Registration

With dynamic events, you can design an application to make programmatic changes to elements in the VI and the VI generates events for these changes. Use the Register for Events node to perform event registration for dynamic events.

Behavior when Dynamically Modifying Event Registration

You can dynamically modify event registration by wiring the event registration refnum output of one Register for Events node to the event registration refnum input of a second Register for Events node. In this configuration, the second Register for Events node inherits the event sources from the first Register for Events node. The following caveats apply to the Register for Events node when you wire its event registration refnum input:

  • You must place the Register for Events node inside an event case.
  • You cannot manually resize or reconfigure the Register for Events node while the event registration refnum input is wired.
  • You must wire the event source 1..n inputs with the same types of references you specified in the Register for Events node that originally created the event registration reference.
  • When you wire an event source 1..n input, Register for Events unregisters the original event source and registers the new event source.
  • Wire a Not A Refnum constant to an event source 1..n input to unregister the original event source without registering a new event source.

Where This Node Can Run:

Desktop OS: Windows

FPGA: This product does not support FPGA devices

Web Server: Not supported in VIs that run in a web application


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