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XSLT <if> Element
The XSLT <xsl:if> element allows you to perform conditional statements against the contents of your XML document. For example, you can present different content only if a given condition is met.
This element can be used in conjunction with the <xsl:for-each> element to present different content depending on the contents of the XML file.
<xsl:if> Example
The Source File
Imagine have an XML file containing a list of food and it's nutritional value. Something like this:
<?xml version="1.0"?>
<food_list>
<food_item type="vegetable">
<name>Agar</name>
<carbs_per_serving>81</carbs_per_serving>
<fiber_per_serving>8</fiber_per_serving>
<fat_per_serving>0.5</fat_per_serving>
<kj_per_serving>1280</kj_per_serving>
</food_item>
<food_item type="vegetable">
<name>Asparagus</name>
<carbs_per_serving>1</carbs_per_serving>
<fiber_per_serving>1</fiber_per_serving>
<fat_per_serving>0</fat_per_serving>
<kj_per_serving>40</kj_per_serving>
</food_item>
<food_item type="vegetable">
<name>Cabbage</name>
<carbs_per_serving>0</carbs_per_serving>
<fiber_per_serving>1</fiber_per_serving>
<fat_per_serving>0</fat_per_serving>
<kj_per_serving>14</kj_per_serving>
</food_item>
<food_item type="vegetable">
<name>Potato</name>
<carbs_per_serving>21.5</carbs_per_serving>
<fiber_per_serving>2</fiber_per_serving>
<fat_per_serving>1</fat_per_serving>
<kj_per_serving>460</kj_per_serving>
</food_item>
<food_item type="vegetable">
<name>Pumpkin</name>
<carbs_per_serving>6</carbs_per_serving>
<fiber_per_serving>1</fiber_per_serving>
<fat_per_serving>0.5</fat_per_serving>
<kj_per_serving>150</kj_per_serving>
</food_item>
<food_item type="vegetable">
<name>Yam</name>
<carbs_per_serving>30.5</carbs_per_serving>
<fiber_per_serving>2</fiber_per_serving>
<fat_per_serving>0.5</fat_per_serving>
<kj_per_serving>550</kj_per_serving>
</food_item>
<food_item type="vegetable">
<name>Zucchini</name>
<carbs_per_serving>1.5</carbs_per_serving>
<fiber_per_serving>1.5</fiber_per_serving>
<fat_per_serving>0.5</fat_per_serving>
<kj_per_serving>55</kj_per_serving>
</food_item>
<food_item type="seafood">
<name>Abalone</name>
<carbs_per_serving>0</carbs_per_serving>
<fiber_per_serving>0</fiber_per_serving>
<fat_per_serving>1</fat_per_serving>
<kj_per_serving>400</kj_per_serving>
</food_item>
<food_item type="seafood">
<name>Barramundi</name>
<carbs_per_serving>0</carbs_per_serving>
<fiber_per_serving>0</fiber_per_serving>
<fat_per_serving>2</fat_per_serving>
<kj_per_serving>390</kj_per_serving>
</food_item>
<food_item type="fruit">
<name>Apple</name>
<carbs_per_serving>15</carbs_per_serving>
<fiber_per_serving>2.5</fiber_per_serving>
<fat_per_serving>0</fat_per_serving>
<kj_per_serving>250</kj_per_serving>
</food_item>
<food_item type="fruit">
<name>Kiwi Fruit</name>
<carbs_per_serving>7.5</carbs_per_serving>
<fiber_per_serving>2.5</fiber_per_serving>
<fat_per_serving>0</fat_per_serving>
<kj_per_serving>150</kj_per_serving>
</food_item>
<food_item type="grain">
<name>Oatbran</name>
<carbs_per_serving>62</carbs_per_serving>
<fiber_per_serving>14</fiber_per_serving>
<fat_per_serving>7</fat_per_serving>
<kj_per_serving>1400</kj_per_serving>
</food_item>
<food_item type="grain">
<name>Wheatgerm</name>
<carbs_per_serving>1.5</carbs_per_serving>
<fiber_per_serving>1</fiber_per_serving>
<fat_per_serving>0.5</fat_per_serving>
<kj_per_serving>70</kj_per_serving>
</food_item>
</food_list>
The Requirement
Now, imagine we're only interested in the vegetables - we only want to display the food that have a type attribute of "vegetable". And, we also want to display it nicely formatted in an HTML table. Something like this:
The Solution
To achieve the above outcome, we use <xsl:for-each> to loop through each "food_item" element, and <xsl:if> to check the value of the "type" attribute (we do this by using the @ symbol - that's how you specify an attribute). If the attribute value equals "vegetable" we output the details.
<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:template match="/">
<xsl:apply-templates/>
</xsl:template>
<xsl:template match="food_list">
<table>
<tr style="background-color:#ccff00">
<th>Food Item</th>
<th>Carbs (g)</th>
<th>Fiber (g)</th>
<th>Fat (g)</th>
<th>Energy (kj)</th>
</tr>
<xsl:for-each select="food_item">
<xsl:if test="@type = 'vegetable'">
<tr style="background-color:#00cc00">
<td><xsl:value-of select="name"/></td>
<td><xsl:value-of select="carbs_per_serving"/></td>
<td><xsl:value-of select="fiber_per_serving"/></td>
<td><xsl:value-of select="fat_per_serving"/></td>
<td><xsl:value-of select="kj_per_serving"/></td>
</tr>
</xsl:if>
</xsl:for-each>
</table>
</xsl:template>
</xsl:stylesheet>
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