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$PARAMETER

Returns the value of the specified class parameter.

Synopsis

$PARAMETER(class,parameter)

Parameters

Argument Description
class Optional — Either a class name or an object reference (OREF) to a class instance. If omitted, uses the object reference of the current class instance. When omitted, you must specify the placeholder comma.
parameter The name of a parameter. An expression which evaluates to a string. The value of the string must match the name of an existing parameter of the class identified by class.

Description

$PARAMETER returns the value of a specified class parameter. $PARAMETER can look up this parameter in the current class context or in a specified class context. You can specify a class name as a quoted string, specify an OREF, or omit the class parameter and take as default the current instance (see $THIS). Specifying class is optional; specifying the comma separator is mandatory.

For example:

  WRITE $PARAMETER("%Library.Boolean","XSDTYPE")
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There are several ways to return the value of a parameter using object syntax, as shown in the following example:

  WRITE "ObjectScript function:",!
  WRITE $PARAMETER("Sample.Person","EXTENTQUERYSPEC")
  WRITE !,"class parameter:",!
  WRITE ##class(Sample.Person).#EXTENTQUERYSPEC
  WRITE !,"instance parameter:",!
  SET myinst=##class(Sample.Person).%New()
  WRITE myinst.%GetParameter("EXTENTQUERYSPEC")
  WRITE !,"instance parameter:",!
  WRITE myinst.#EXTENTQUERYSPEC
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Invalid Values

  • $PARAMETER("","XMLTYPE"): attempting to invoke an invalid OREF (such as the empty string, an integer, or a fractional number) results in an <INVALID OREF> error.

  • $PARAMETER("bogus","XMLTYPE"): attempting to invoke a nonexistent class results in a <CLASS DOES NOT EXIST> error, followed by the specified class name. If a package name is not specified, InterSystems IRIS assumes the default. For example, attempting to invoke the nonexistent class “bogus” results in the error <CLASS DOES NOT EXIST> *User.bogus.

  • $PARAMETER(,"XMLTYPE"): attempting to default to the current object instance when none has been established results in a <NO CURRENT OBJECT> error.

  • $PARAMETER("%SYSTEM.Task",""): attempting to reference an invalid parameter name (for example, an empty string) or to reference a parameter by number generates an <ILLEGAL VALUE> error.

  • $PARAMETER("%SYSTEM.Task","MakeCoffee"): attempting to reference a nonexistent parameter name returns the empty string ("").

Examples

The following example specifies class names and returns the class default values for the XMLTYPE and XSDTYPE parameters:

  WRITE $PARAMETER("%SYSTEM.Task","XMLTYPE"),!
  WRITE $PARAMETER("%Date","XSDTYPE")
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The following example specifies an OREF and returns the value of the XMLTYPE parameter for this instance:

  SET oref=##class(%SYSTEM.Task).%New()
  WRITE $PARAMETER(oref,"XMLTYPE")
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The following example returns a system parameter using $PARAMETER syntax and using class syntax:

  WRITE $PARAMETER("%SYSTEM.SQL","%RandomSig"),!
  WRITE ##class(%SYSTEM.SQL).#%RandomSig
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See Also