TOPICS
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TOPICS
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Programmatic Control of User
Interface
A. VI Server
B. Property and Invoke Nodes
C. Implicitly and Explicitly Linked Property and Invoke
Nodes
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A. VI Server
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VI Server
LabVIEW organizes and operates on its parts (front panel,
button, arrays, etc.) within an architecture called VI Server, which
is object oriented.
Terminology
:
• A class defines what an object is able to do, what operations it
can perform (methods), and what properties it has.
• An object is a member of a class.
• Properties are the attributes of an object.
• Methods perform an operation on an object.
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VI Server—Class Hierarchy
VI
Application
Generic
GObject
Control
Boolean
Cluster
Etc.
Etc.
Generic
GObject
Control
Boolean
Pets
Dogs
Labrador
Poodle
Cats
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B. Property and Invoke Nodes
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Property Nodes
• They read and write the properties
of an object.
• They allow you to make these
modifications programmatically.
• There are two types of Property Nodes:
– Implicitly linked
– Explicitly linked.
• They can have multiple properties and execute from top to
bottom.
– By default, if an error occurs on one of the terminals, the rest does not
execute and error is output at error out terminal.
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Invoke Nodes
•
Use the Invoke Node to perform actions, or methods, on
referenced items (VIs, controls).
•
Methods can have parameters or return values.
•
There are two types of Invoke Nodes:
−
Implicitly linked
−
Explicitly linked.
Method Name
Parameters
DEMONSTRATION
Creating Property and Invoke Nodes
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C. Implicitly and Explicitly
Linked Property and Invoke
Nodes
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Implicitly and Explicitly Linked
Invoke/Property Nodes
Explicitly Linked
(requires reference)
Implicitly Linked
(color/ label for data type/label)
Property
Node
Invoke
Node
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VI
VI
Main VI
Main VI
SubVI
Implicitly Linked Property Node
Explicitly Linked Property Node
Control References
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SubVI Front Panel
SubVI Block Diagram
Edit»
Create
SubVI
1. Select the portion of
the block diagram that
will be in the subVI.
2. Select Edit»Create
SubVI; LabVIEW
automatically creates
the control references
needed for the subVI.
SubVIs and Invoke/Property Nodes
DEMONSTRATION
Creating References for Property
and Invoke Nodes; Selecting a Class