CODEWITHSUNDEEP
xslt
toomanyairmiles
toomanyairmiles

Reputation: 6485

Conditional statements in xsl

I working on a site which some if/or statements in XSL and being a little unfamilar with the language i'm not certain how to accomplish:

if [condion one is met] or [condition two is met] then do [action] otherwise do [alternative action]

can anyone offer some examples?

Thanks in advance!

Upvotes: 21

Views: 57360

Answers (4)

Tomalak
Tomalak

Reputation: 338208

Conditionals in XSLT are either an unary "if":

<xsl:if test="some Boolean condition">
  <!-- "if" stuff (there is no "else" here) -->
</xsl:if>

or more like the switch statement of other languages:

<xsl:choose>
  <xsl:when test="some Boolean condition">
    <!-- "if" stuff -->
  </xsl:when>
  <xsl:otherwise>
    <!-- "else" stuff -->
  </xsl:otherwise>
</xsl:choose>

where there is room for as many <xsl:when>s as you like.

Every XPath expression can be evaluated as a Boolean according to a set of rules. These (for the most part) boil down to "if there is something -> true" / "if there is nothing -> false"

  • the empty string is false
  • 0 is false (so is NaN)
  • the empty node set is false
  • the result of false() is false
  • every other literal value is true (most notably: 'false' is true and '0' is true)
  • the result of expressions is evaluated with said rules (no surprise here)

Edit: There is of course a more advanced (and more idiomatic) method to control program flow, and that's template matching:

<xsl:template match="node[contains(., 'some text')]">
  <!-- output X -->
</xsl:template>

<xsl:template match="node[not(contains(., 'some text'))]">
  <!-- output Y -->
</xsl:template>

<xsl:template match="/">
  <xsl:apply-templates select=".//node" />
</xsl:template>

Writing templates that match specific nodes and using <xsl:apply-templates> to make the XSLT processor choose the appropriate ones is superior to writing complex <xsl:if> or <xsl:choose> constructs.

The above sample is equivalent to the imperative style:

<xsl:template match="/">
  <xsl:for-each select=".//node">
    <xsl:choose>
      <xsl:when test="contains(., 'some text')">
        <!-- output X -->
      </xsl:when>
      <xsl:when test="not(contains(., 'some text'))">
        <!-- output Y -->
      </xsl:when>
    <xsl:choose>
  <xsl:for-each>
</xsl:template>

XSLT beginners tend to pick the latter form for its familiarity, but examining template matching instead of using conditionals is worthwhile. (also see.)

Upvotes: 44

Daniel F. Thornton
Daniel F. Thornton

Reputation: 3685

XSL has an <xsl:if>, but you're probably looking more for a <xsl:choose> / <xsl:when> / <xsl:otherwise> sequence. Some examples here (near the bottom). Maybe:

<xsl:choose>
    <xsl:when test="[conditionOne] or [conditionTwo]">
        <!-- do [action] -->
    </xsl:when>
    <xsl:otherwise>
        <!-- do [alternative action] -->
    </xsl:otherwise>
</xsl:choose>

Upvotes: 4

Flyer1
Flyer1

Reputation: 847

The general if statement syntax is

<xsl:if test="expression">
  ...some output if the expression is true...
</xsl:if>

Not sure if XSL has the else condition but you should be able to test if true then test if false or the other way around.

Upvotes: 1

Zack The Human
Zack The Human

Reputation: 8481

In this case you would have to use a xsl:choose. It's like using if/else with a final else.

<xsl:choose>
  <xsl:when test="condition one or condition two">
    <!-- action -->
  </xsl:when>
  <xsl:otherwise>
    <!-- alternative action -->
  </xsl:otherwise>
</xsl:choose>

Upvotes: 0

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