Variable types

A variable type is a model variable from which you can create instances of the variable. Variable instances can contain other specific variables.

Predefined and custom variable types

Each project contains these predefined variable types:

Variable

Analog variable

Dynamic links

Node pointer

Tag variable types (Communication driver objects)

Custom variable types that you or the application logic create are available only in the project in which you create them.

TIP: Changes to a variable type automatically apply to all instances of the variable. If you delete the variable type, you also delete all the subtypes of the variable type, along with the corresponding instances of the variable.

Variable

Variables contain specific data types (for example, a numeric Int32 value or a String value).

By default, every variable contains these attributes:

Attribute	Description
BrowseName	Name of the variable in the project.
DataType	Data type that the variable can contain.
Description	Description of the variable.
DisplayName	Translatable variable name that can appear on the interface at runtime.
NodeId	Automatically assigned unique identifier.
Value	Value of the data.

For example, you can create a label with a string value of

and then create a dynamic link between the variable and the

Text

property of a

Button

object.

Dynamic link between the Text property of a button and the string variable

Analog variable

Analog variables are structured variables that represent physical characteristics and ranges.

By default, every analog variable contains these attributes:

Attribute	Property	Data type	Description
EngineeringUnits TIP: The dynamic link window displays the EngineeringUnits variable type. See Develop a label with a localized engineering unit and Develop a gauge with a localized engineering unit.	Description	Localized text	Description of the unit of measurement.
	DisplayName	Localized text	Name of the unit of measurement.
	UnitId	Int32	Numeric unit of measurement.
EURange	Lower limit	Double	Lower limit of the range of values for the variable.
	High Limit	Double	Upper limit of the range of values for the variable.
	Constrain	Boolean	If True: Values out of range of not accepted and the previous value is retained. If False: Values out of range are accepted.

For example, you can create a constrained linear gauge that sources data from a constrained variable. See Develop a constrained linear gauge.

Constrained linear gauge that sources data from the analog variable (runtime)

Node pointer

Node pointers references nodes in the project.

The referenced node must be of the type and class defined by these properties:

Property	Data type	Description
Kind	NodeId	Type of object or type of variable from which the node is derived
NodeClass	NodePointerNodeClass	Instance . The node can be only an instance Type . The node can be only a typ Any . The node can be an instance or a type

For example,

Data logger

objects have

Store

node pointer properties.

Node pointer that targets database objects

Variables

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