XPathError class

An XPathError exception can be thrown by various methods in the XmlDoc API. It indicates an error either in the syntax of an XPath argument to the method, or in the results returned by that XPath expression. The various read-only properties of an XPathError object (which can be set by the Catch statement) provide information about the failed operation.

An example of using the XPathError exception is:

%err Object XPathError Try %d:Print('a b c') Catch XPathError To %err PrintText {~} = {%err:Reason} PrintText {~} = {%err:Description} PrintText {~} = {%err:CharacterPosition} End Try

Since the expression in the above invocation of the Print method (a b c) is not a valid XPath expression, the above fragment will result in the following:

%err:Reason = SyntaxError %err:Description = Expect "/" for new step or "[" for predicate %err:CharacterPosition = 3

This class is new in version 7.8 of the Sirius Mods.

The XPathError methods

The following are the available XPathError class methods.

Method	Description
CharacterPosition	Position of character at of before which the error occurred
Description	Brief description of the exception
New	Create a new XPathError object
Reason	Enumerated cause of the exception

The methods in the class are described in the subsections that follow. In addition:

• "Notation conventions for methods" has information about the conventions followed.
• "XPathError methods syntax" is a single page that contains the syntax diagrams of all the methods in the class.

CharacterPosition property

Position of character at of before which the error occurred (XPathError class)

[Introduced in Sirius Mods 7.8]

Syntax

%number = xPathError:CharacterPosition

Syntax terms

%number	The position of the character at which the exception was thrown.
xPathError	An XPathError object.

Description property

Brief description of the exception (XPathError class)

[Introduced in Sirius Mods 7.8]

Syntax

%string = xPathError:Description

Syntax terms

%string	A string to receive the description of the exception.
xPathError	An XPathError object.

New constructor

Create a new XPathError object (XPathError class)

[Introduced in Sirius Mods 7.8]

Each argument to New sets the value of the corresponding property of the newly constructed XPathError object.

Syntax

%xPathError = [%(XPathError):]New( Reason= xPathErrorReason, - [Description= string], - [CharacterPosition= number])

Syntax terms

%xPathError	A reference to an instance of an XPathError object.
%(XPathError)	The class name in parentheses denotes a shared method.
Reason	This name required parameter is an XPathErrorReason enumeration value (see "Usage notes", below) which specifies the value to be assigned to the exception object's Reason property. The Reason parameter is not optional.
Description	This name required parameter specifies the string value (string) to be assigned to the object's Description property.
CharacterPosition	This name required parameter specifies the numeric value (number) to be assigned to the object's CharacterPosition property.

Reason property

Enumerated cause of the exception (XPathError class)

[Introduced in Sirius Mods 7.8]

Syntax

%xPathErrorReason = xPathError:Reason

Syntax terms

%xPathErrorReason	This XPathErrorReason enumeration value (see "Usage notes", below) describes the reason for the translation failure.
xPathError	An XPathError object.

Usage notes

An XPathErrorReason enumeration may have one of the following values:

SyntaxError	A violation of the syntax of an XPath expression.
EmptyResult	No nodes are matched by the XPath expression, and the method requires at least one matching node.

As with all enumerations, you use the ToString method to convert an enumeration value to a character string whose value is the name of the enumeration value.