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Wait on Notification with Notifier History (G Dataflow)

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    Last Modified: March 15, 2017

    Waits until a notifier receives a notification and returns the notification.

    This node tracks the most recent notification and timestamp for each individual notifier when you use this node repeatedly with different notifiers. If a notifier reference becomes invalid because another node releases it, this node stops waiting and returns an error.

    For an array of notifier references, use Wait on Notification from Multiple with Notifier History instead.

    Programming Patterns

    Use Send Notification to send a notification to this node.

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    notifier

    A reference to a notifier.

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    ignore previous

    A Boolean value that determines whether to ignore notifications that are sent to the notifier before this node executes.

    True If the notifier contains a notification before this node executes, this node ignores the previous notification and waits until the notifier receives another notification.
    False If the notifier contains a notification that was sent before this node checks for it, then this node does not wait.

    How Do Message Timestamps Affect Behavior?

    Each unique instance of this node remembers the timestamp of the last notification it receives.

    If ignore previous is set to True, this node always waits for a new notification, even if the notification currently in the notifier is one it has never seen before.

    If ignore previous is set to False, each instance of this node waits if the notification in the notifier has a timestamp for the same time that the instance of the node last executed. If the notification is new, then this node returns the notification in the notification output.

    Default: False

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    timeout in milliseconds

    Number of milliseconds that the node waits for the notifier to receive a message before timing out.

    Default: -1 — The node never times out.

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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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    notifier out

    Reference to the notifier.

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    notification

    The last message the notifier receives.

    The data type of this output changes to match the data type of the notifier.

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    timed out?

    A Boolean that indicates whether the notifier received a notification before the node timed out or an error occurred.

    True The notifier did not receive a notification before the node timed out, or this node generated an error.
    False The notifier received a notification, or an error occurred before this node executed.
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    error out

    The node produces this output according to standard error behavior.

    This node can return the following error codes.

    1122 The reference became invalid while the node was waiting for it.
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    Note  

    This is not a comprehensive list of errors this node can return.

    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.

    Advantages and Disadvantages of Maintaining Notifer History

    Maintaining notifier history prevents dropped notifications. For example, when you use this node in a loop with multiple arrays of notifier references, this node tracks all of the notifications that it receives for each notifier. However, maintaining notification history also uses more resources than only storing the most recent notification. If your code requires faster execution than this node achieves, use Wait on Notification instead.

    Removing Notifications

    This node does not remove the notification from the notifier. The notification remains in the notifier until all Wait on Notification nodes return the notification. While the notification remains in the notifier, each Wait on Notification node will return a given notification only one time. If you want to remove a notification from a notifier before all Wait on Notification nodes return the notification, use Cancel Notification.

    Where This Node Can Run:

    Desktop OS: Windows

    FPGA: This product does not support FPGA devices


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