8 Global Variables

A variable declaration consists of the keyword variable, the data type, the variable identifier and the terminator ;. In one declaration more than one variables of the same data type can be defined. In this case the identifiers of the variables have to be separated by , (commas).

If a variable is declared and not within a rule or method (see also chapter “Local Variables”), it is called a global variable.

In IDM global variables are treated like objects so that not only the content of a variable but the variable itself can be changed at runtime (see chapter “Attributes of Global Variables that Can Be Changed Dynamically”).

8.1 Variable Definition

Syntax

{ export | reexport } variable <data type> <variable name>
  [ , <variable name> ] ;

The following data types are available:

Data type	Value Range
anyvalue	Arbitrary, undefined data type; will be defined only by actual occupation.
attribute	Attribute data type in the IDM.
boolean	Boolean value (true \| false).
datatype	IDM data type.
class	Class of an object, e.g. "window".
enum	Symbolic constant; enumeration type for special attributes, e.g. "sel_row".
event	Type of event, e.g. "select".
index	Index value for 2-dimensional attributes [I,J].
integer	Integral number ("long integer"), e.g. 42.
method	Method, e.g. "delete".
object	Object in the sense of the IDM (actual objects, resources, functions, rules,…).
pointer	Pointer from the application.
string	Character string which can be arbitrarily long (zero terminated), e.g. "hello".
void	Data type without value.

8.2 Variable Definition with Initialization

The following definition initializes the generated variable immediately with a value. The data type of the value has to be identical with the data type of the variable.

Syntax

{ export | reexport } variable <data type> <variable name> := <value>
  [ , <variable name> := <value> ] ;

Object references, numbers, colors, strings, and boolean values, i.e. anything which is supported by the ISA Dialog Manager, can be stored in variables of the type anyvalue.

Example

variable integer Filling_level;

variable boolean Valve_state := true;

variable string Valve_identifier := "main valve";

variable enum Mode;

variable object PbSwitch; // Let PbSwitch be a pushbutton

A character string is always in quotation marks.

Valve_identifier := "main valve";

In this example the words "main valve" are a string.

8.3 Configurable Variables

The additional keyword config marks a global variable as configurable, i.e. its value can be set in a configuration file.

Syntax

{ export | reexport } { config } variable <data type>
  <variable name> { := <value> } [ , <variable name> { := <value> } ] ;

The configuration file is loaded with the functions loadprofile(), DM_LoadProfile or DMcob_LoadProfile.

8.4 Protecting Variables against Changes

Changes to the content of a global variable can be prevented by using the keyword constant instead of variable in the declaration or by setting the attribute .constant of the variable to true.

Syntax

{ export | reexport } constant <data type> <variable name> := <value>
  [ , <variable name> := <value> ] ;

8.5 Attributes of Global Variables that Can Be Changed Dynamically

The table below shows those attributes of variables, that can be queried and changed dynamically at runtime.

Attribute	Value Range	Meaning
.value	anyvalue	Value
.type	datatype	Data type
.constant	boolean	Changeability of content

In order to refer to the variable itself and not to its content the attribute .self is used. This is followed by the attribute that shall be addressed.

Example

variable integer I := 2;

print I.self.type // integer

print I.self.value // 2

I.self.type := boolean;

print I.self.type; // boolean

Note

This applies to global variables only and not to local variables (i.e. variables declared within rules and methods).