Elements of a Qapp

Contents

The fundamental element of a Qapp is called a node. Each node contains specific attributes and connects logically.

Example: Nodes in a Qapp Editor

Nodes in the Qapp Editor

The Qapp Editor has two types of tabs:

▪Execution Flow tab — define the execution sequence of the nodes within a Qapp, as well as the relations or conditions among the nodes.

oStart — the starting point of a Qapp. You can define the way of the Qapp to obtain devices at runtime within this node.

oStop — the endpoint to terminate a Qapp. You can define a message and the message will prompt when the Qapp executes this node.

▪Canvas tab — contain an internal workflow composed of multiple subnodes as follows.

The context menu in the Qapp Editor is as follows:

Icon	Description
	Save the Qapp.
	Save as another Qapp.
	Run the Qapp.
	More operations, such as customizing functions and locking the Qapp.

The following table introduces the system built-in variables in a Qapp.

Variable Name	Description
$_device	A global PyDevice object representing the device on which the Qapp is running. It is a simple PyDevice object and not an array of PyDevice objects. The Qapp automatically loops through each of the selected devices.
$_device_queue	A variable representing the device queue table that the Qapp loops through.
$_command	The command on which the output is based.

Variable Name

Description

$_device

A global PyDevice object representing the device on which the Qapp is running.

It is a simple PyDevice object and not an array of PyDevice objects. The Qapp automatically loops through each of the selected devices.

$_device_queue

A variable representing the device queue table that the Qapp loops through.

$_command

The command on which the output is based.

For more built-in variables, refer to the Global Data Repository (GDR).