Load Value
| Block Group: | Data Services |
| Icon: | no icon |
The Load Value block retrieves information about the value of a data node.
To automatically create a Load Value block for a node at a particular path, you can drag that node from the Metrics panel into the dataflow window.
For information on using dataflow blocks, see Dataflow.
Input/Output Properties
The following properties of the Load Value block can take input and give output.
- path (string)
- subpath (string)
- enabled (boolean)
- qos (enum)
- format (string)
path specifies the node for which to return information.
subpath (optional) is appended to path, separated by /, to form the node path.
enabled specifies whether the Load Value block updates when the node’s value changes. The default is TRUE.
qos determines persistence. qos values other than 0 apply only to DSA data; for other data services, 0 is used.
- 0 (default)—The real-time value is loaded and is replaced with new values in real time.
- 1—The real-time value is loaded, is output in a table, and is replaced with new values in real time. If more than one value is loaded in a request, multiple rows appear in the table. The output is intended to be used with a threaded dataflow repeater in "stream" mode.
- 2—Intended only for remote dataflow. The real-time value is loaded, is output in a table, and is replaced with new values in real time. Only one row appears in the table. If the connection is lost, values persist on the server, and the most recent value is sent to the client when the connection is restored.
- 3—Intended only for remote dataflow. The real-time value is loaded, is output in a table, and is replaced with new values in real time. If more than one value is loaded in a request, multiple rows appear in the table. If the connection is lost, values persist on the server, and all values stored on the server are sent to the client when the connection is restored. The output is intended to be used with a threaded dataflow repeater in "stream" mode.
For a qos of 1, 2, or 3, you can access table cells by binding the value property to a Table block. The table has timestamp and value columns.
format specifies a format string applied to the value. The result is returned in formatted. Text in square brackets is replaced:
[value],[unit],[status]and other fields of the value update are replaced by their values.[value.key]reads a key (or index) of a map or list value.[$config]and[@attribute]are replaced by a DSA config or attribute of the node.[auto]or[formatted]is replaced by the default formatted value.- A number pattern, such as
[0.00]or[#,##0], formats the numeric value.
If format is blank, the default formatting is used.
Output Properties
The following properties of the Load Value block can give output but cannot take input.
- value (any)
- unit (string)
- formatted (string)
- status (string)
- error (string)
- lastUpdate (string)
value returns the current value of the node, if enabled is TRUE. Returns the last collected value of the node, if enabled is false. If the value is a table on a DSA node, the table is loaded and returned.
unit returns the units of the node.
formatted returns the value formatted by format. If format is blank, for example, for a numeric value, it returns a string that includes units. For an enum or boolean value, it returns the string associated with the value.
status returns the status of the node, if applicable, such as “down” or “overridden.”
error returns the error message, if any.
lastUpdate returns a string indicating when the node was last updated.
Example
The following image demonstrates how to create a Load Value block by dragging a node to the dataflow window.
