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Owning Palette: Application Control VIs and Functions
Requires: Base Development System
Gets (reads) and/or sets (writes) properties of a reference. Use the property node to get or set properties and methods on local or remote application instances, VIs, and objects. You also can use the Property Node to access the private data of a LabVIEW class.
The Property Node automatically adapts to the class of the object that you reference. LabVIEW includes Property Nodes preconfigured to access XML Properties, VISA properties, .NET properties, and ActiveX properties.
|reference is the refnum associated with the object for which you want to set or get properties. If the Property Node class is Application or VI, you do not have to wire a refnum to this input. For the Application class, the default is the current application instance. For the VI class, the default is the VI containing the Property Node.
You also can wire a LabVIEW class to the reference input to access the private data of the LabVIEW class.
|error in describes error conditions that occur before this node runs. This input provides standard error in functionality.|
|property 2..n are examples of properties you want to set (write).|
|reference out returns reference unchanged.|
|error out contains error information. This output provides standard error out functionality.|
|property 1..n are examples of properties you want to get (read).|
To select the class on which to execute the property, wire the refnum to the reference input. For example, to select the VI, Generic, or Application class, wire the VI, VI object, or application reference to the reference input. The node adapts to the class automatically. You also can right-click the node and select a class from the shortcut menu.
You can wire a LabVIEW class to the reference input of a Property Node. If the LabVIEW class has accessor VIs that you can access through a Property Node, you can read from or write to the accessor VIs using a Property Node.
You can quickly view the implementation of a LabVIEW class property if the block diagram of the accessor VI is available. To view the implementation of a LabVIEW class property, right-click the property and select Open Accessor VI from the shortcut menu. If the property is dynamic with more than one implementation, selecting this option displays the Choose Implementation dialog box. Use this dialog box to view all implementations of the property, or dynamic dispatch member VI, and open one or more implementations.
|Note If you do not wire the Property Node, the class property still executes at run-time.|
If the Property Node opens and returns a reference to an object, use the Close Reference function to close the reference.
Move the cursor over terminals in the Property Node to display more information about the property in the Context Help window. You also can right-click a property terminal and select Help For Property from the shortcut menu, where Property is the name of the property.
You can read or write multiple properties using a single node. However, some properties are not readable and some are not writable. Use the Positioning tool to resize the Property Node to add new terminals. A small direction arrow to the right of the property indicates a property you read. A small direction arrow to the left of the property indicates a property you write. Right-click the property and select Change to Read or Change to Write from the shortcut menu to change the operation of the property.
The node executes from top to bottom. The Property Node does not execute if an error occurs before it executes, so always check for the possibility of errors. If an error occurs in a property, LabVIEW ignores the remaining properties and returns an error. If you right-click the Property Node and select Ignore Errors Inside Node, LabVIEW executes the remaining properties on the Property Node. Only the first error is returned by the Property Node. The error out cluster contains information about which property caused the error.
Properties have a short or long name that you can change by right-clicking and selecting Name Format from the shortcut menu. The No Names format displays only the data type for each property.
|Note You can right-click the Property Node and select Downcast to Class from the shortcut menu to typecast a reference to a more specific class in the inheritance hierarchy. For example, select Downcast to Class from an Interchangeable Virtual Instruments (IVI) class driver to view the IVI specific driver properties. This item is not supported for all class types. If Downcast to Class is disabled, you can use the To More Specific Class and To More Generic Class functions.|