6/6/2016 3:23 PM 1 of 15

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1 6/6/2016 3:23 PM 1 of 15

2 6/6/2016 3:23 PM 2 of 15 2) XSLT Selection XSLT allows for selection with two statements xsl:if chooses to do or not to do (very basic) xsl:choose chooses from several alternatives and a default

3 6/6/2016 3:23 PM 3 of 15 3) Background well-formed XML HTML XSLT processing model XPath xsl:value-of xsl:for-each (optional)

4 6/6/2016 3:23 PM 4 of 15 4) <xsl:if> element The basic structure of the IF construct in XSLT is <xsl:if test=" (condition) ">... </xsl:if> The (condition) is an XPath predicate. If there is no test in it, it is an existence test. XPath functions and comparisons let us test many things.

5 6/6/2016 3:23 PM 5 of 15 5) <xsl:if> example Note the XPath in the conditional statement below <xsl:if test="/members/member[3]/member_data/ <b>balance due!</b> </xsl:if> < needed to do a < comparison does a number comparison since the 0 is a number literal

6 6/6/2016 3:23 PM 6 of 15 6) <xsl:choose> element The xsl:choose lists 1 or more alternatives and an optional default: <xsl:choose> <xsl:when test=" (condition) ">... </x <xsl:when test=" (condition) ">... </x... as many as you like... <xsl:otherwise>... </xsl:otherwise> <! </xsl:choose> Same (condition) as the xsl:if test. The first when with a true condition is done, then the choose is exited.

7 6/6/2016 3:23 PM 7 of 15 7) <xsl:choose> example Current context is members/member (inside a template or for-each) <xsl:choose> <xsl:when test="name/last = 'Jones'"> Jones (could be an alias!) </xsl:when> <xsl:otherwise> <xsl:value-of select="name/last"/> </xsl:otherwise> </xsl:choose> = does a comparison. The embedded quotes in the test have to be the other kind, or use the named entity " or &apos;.

8 6/6/2016 3:23 PM 8 of 15 8) Comparisons in XPath XPath has these built-in comparisons: =!= : Equal / Not equal > >= : Greater / Greater or equal < <= : Less / Less or equal "<" is a reserved character in XML, so you must use < when you want to do a less-than comparison.

9 6/6/2016 3:23 PM 9 of 15 9) Numbers vs. Text Since XML documents are saved as text, numbers must be converted to values with the number() function number evaluates the XPath then converts the result to a number <xsl:if test="number(/members/member[3]/member_d < 0"> <b>balance due!</b> </xsl:if> If being compared to a number literal, XPath does the number() call for you Available math operators: +, -, *, div, mod Math functions include: ceil(), floor(), round()

10 6/6/2016 3:23 PM 10 of 15 10) Test for nodes To test for the existence of a node, just provide the XPath If a node exists, satisfies the if test <xsl:if test="/members/member[3]"> <xsl:value-of select="/members/member[3]/ </xsl:if>

11 6/6/2016 3:23 PM 11 of 15 11) Manipulate text in XPath XPATH has many string functions, here are some: name() : returns the name of the node text() : returns the text within the node string(arg) : converts arg to a string (from substring(string,start,length) : portion of t start+length-1. If length omitted, re string-length(string) : returns the length of These can be used to pull apart strings, test portions, and evaluate complex conditions by building them up.

12 6/6/2016 3:23 PM 12 of 15 12) Look where you are XPATH has useful functions related to where you are in the XML structure. position() : position of the current node wit last() : position of the last node in the nod count() : number of nodes in the node set text() : text within the nodelast() : returns name() : returns the name of the node node() : matches any node (of the 7 types of these are useful for positional checks like firstin-the-list or last-in-the-list

13 6/6/2016 3:23 PM 13 of 15 13) Review Use xsl:if with a test to take an action when it is true Use xsl:choose for multiple cases or alternative (xsl:otherwise) Test with the basic comparison operators Use < for the "<" character since it is a reserved XML character Values need to be converted to numbers with the number() function to be numerically compared Test for the existence of a node Test for values in strings, node position, and more with XPath functions

14 6/6/2016 3:23 PM 14 of 15 14) Resources W3schools on xsl:if at /xsl/xsl_if.asp W3schools on xsl:choose at XSLT/XPath 1.0 Quick Reference Guide at

15 6/6/2016 3:23 PM 15 of 15 15) Your Turn If there is more than one, put a... after the first one to show there's more If it's not the last one, put a, after it (use in xsl:for-each for building up lists) List members with negative balances (uses xsl:if in xsl:for-each) Display a member's name, and if they left a note and the date they left (target a member with indexing, or do all in a xsl:for-each) (pudding.xml) Print a message based on calories: <100, "great for snacks"; <200, "ok for snacks"; otherwise, "not snack food" (uses xsl:choose)