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Executing Code Based on a User Event

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    Last Modified: September 25, 2017

    User events are defined on the diagram and triggered by the execution of diagram code. Unlike user interface events, which require direct user interaction with front panel objects, user events allow you to create an application that responds to programmatic changes on objects. Additionally, you can handle data associated with the event in its case of the Event Structure.

    What to Use

    What to Do

    Create the following diagram to build a user event that notifies the Event Structure to handle the event and any associated data.

    Customize the gray sections for your unique programming goals.

    To define a user event, wire a constant of the same data type as the event to Create User Event.

    The input for Create User Event is an individual element or a cluster whose data type defines the data type for the event.

    Create User Event returns a reference to the user event that you create. Use this reference to register for events and generate a user event.

    To give a unique name to the user event you create, select Create User Event and edit the Event name field on the Item tab. This name appears in the Select Handled Events dialog box of an Event Structure. In this diagram, the name of the user event is My User Event.

    Use Register For Events to dynamically register the user event. You must dynamically register the user event so that the Event Structure can handle it when it occurs.

    To display the Dynamic Event Terminal, click the Event Structure and select Use dynamic events on the Item tab. Wire the event registration refnum output of Register For Events to the Dynamic Event Terminal on the left side of the Event Structure.

    The user event data items appear in the Event Data Node on the left border of the Event Structure.

    Use the Select Handled Events dialog box to configure a case in the Event Structure to handle the event.

    The name of the user event appears under the Dynamic subheading in the Select Handled Events dialog box.

    Use the Event Data Node to access data elements associated with a particular event.

    To add more data items to the Event Data Node, vertically resize the node.

    Use Generate User Event to broadcast the user event you wire to this node and the associated event data to each Event Structure registered to handle the event.

    The data value that you wire to this node must match the data type of the user event.

    spd-note-note
    Note  

    If the user event is not registered, Generate User Event has no effect. If the user event is registered but no Event Structure is waiting on it, the VI queues the user event and data until an Event Structure executes to handle the event.

    To conserve memory resources, use Unregister For Events and Destroy User Event to release the associated events and the user event reference.
    Create code that executes whenever this user event occurs.

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