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You are here: Popular Formats > XML (Extensible Markup Language) Reader/Writer > xfMap > More Expression Elements > selexpr Expressions
selexpr Expressions
The selexpr expression returns the first, last, or the ith non-empty evaluated expression sequence from its argument list. It is represented in the xfMap document with the <selexpr> element, and it has the following general form:
<selexpr expr=”...”> <arg> <!-- some expression sequence --> </arg> <arg> <!-- some expression sequence --> </arg> ... <arg> <!-- some expression sequence --> </arg> </selexpr>
The expression string (i.e., the expr attribute) specifies the first, last, or ith evaluated non-empty expression sequence to be returned. The valid values for the expression string are first, last, or a positive integer between 1 and k, where k is the number of arguments.
Example
items.xml
<?xml version=”1.0”?> <items> <item> <primary-id>p9384</primary-id> <alternate-id></alternate-id> </item> <item> <primary-id></primary-id> <alternate-id>a2046</alternate-id> </item> <item> <primary-id></primary-id> <alternate-id></alternate-id> </item> </items>
selexpr.xmp
<?xml version=”1.0”?> <xfMap> <feature-map> <mapping match=”item”> <feature-type> <selexpr expr=”first”/> <arg> <extract expr=”./primary-id”/> </arg> <arg> <extract expr=”./alternate-id”/> </arg> <arg> <literal expr=”no-id”/> </arg> </selexpr> </feature-type> </mapping> </feature-map> </xfMap>
FME features constructed:
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Feature Type: `p9384' Attribute(string): `xml_type' has value `xml_no_geom' Geometry Type: Unknown (0) =================================================================== +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Feature Type: `a2046' Attribute(string): `xml_type' has value `xml_no_geom' Geometry Type: Unknown (0) =================================================================== +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Feature Type: `no-id' Attribute(string): `xml_type' has value `xml_no_geom' Geometry Type: Unknown (0) ===================================================================