- The XSL Elements
- The xsl:if Element
- The xsl:choose, xsl:when, and xsl:otherwise Elements
- The xsl:eval Element
- Summary
- Q&A
The xsl:choose, xsl:when, and xsl:otherwise Elements
The previous example showed you how to use multiple <xsl:if> elements in situations where there are alternatives. Although this works, it's ungainly when there are several possible values. In that case, it's better to use a combination of the <xsl:choose>, <xsl:when>, and <xsl:otherwise> elements. The following two sections illustrate how these elements are used.
An xsl:choose and xsl:when Example
Reopen listing14-4.xml and change these lines:
<Book> <Title>Teach Yourself Uses of Silicon in 24 Hours</Title> <Author> <Name>Missy Fixit</Name>
to these lines:
<Book BestSeller="impossible"> <Title>Teach Yourself Uses of Silicon in 24 Hours</Title> <Author> <Name>Missy Fixit</Name>
Add the following two additional records that appear in Listing 15.3 to the end of the file. Save the updated file as listing15-3.xml.
Listing 15.3 Two Records with Additional Values for the BestSeller Attribute
1: <Book BestSeller="guaranteed"> 2: <Title>101 Unusual Uses for Hairspray</Title> 3: <Author> 4: <Name>Harpo Hair</Name> 5: <Address>101 Furrball</Address> 6: <City>Clipper City</City> 7: <State>California</State> 8: <PostalCode>10102</PostalCode> 9: <Country>United States</Country> 10: <Phone>(586) 212-3498</Phone> 11: <Email>HairX@HairClip.com</Email> 12: <URL>http://www.HairClip.com</URL> 13: </Author> 14: <Publisher> 15: <Name>Sams Publishing</Name> 16: <Address>201 West 103rd Street</Address> 17: <City>Indianapolis</City> 18: <State>Indiana</State> 19: <PostalCode>46290</PostalCode> 20: <Country>United States</Country> 21: <Phone>(111) 123-4567</Phone> 22: <Editor>Dummy Name</Editor> 23: <EmailContact>Dummy.Name@samspublishing.com</EmailContact> 24: <URL>http://www.samspublishing.com</URL> 25: </Publisher> 26: <ISBN>0-578-3411-0</ISBN> 27: <PublisherBookID>1234576</PublisherBookID> 28: <PublicationDate>2000-03-01</PublicationDate> 29: <Price>36.95</Price> 30: </Book> 31: <Book BestSeller="dud"> 32: <Title>Celebrity Toenail Clippings</Title> 33: <Author> 34: <Name>Foot Lover</Name> 35: <Address>101 Podiatrist Center</Address> 36: <City>Clipper City</City> 37: <State>California</State> 38: <PostalCode>10102</PostalCode> 39: <Country>United States</Country> 40: <Phone>(586) 212-2112</Phone> 41: <Email>Exotic@CToesClip.com</Email> 42: <URL>http://www.CToesClip.com</URL> 43: </Author> 44: <Publisher> 45: <Name>Sams Publishing</Name> 46: <Address>201 West 103rd Street</Address> 47: <City>Indianapolis</City> 48: <State>Indiana</State> 49: <PostalCode>46290</PostalCode> 50: <Country>United States</Country> 51: <Phone>(111) 123-4567</Phone> 52: <Editor>Dummy Name</Editor> 53: <EmailContact>Dummy.Name@samspublishing.com</EmailContact> 54: <URL>http://www.samspublishing.com</URL> 55: </Publisher> 56: <ISBN>0-578-3001-0</ISBN> 57: <PublisherBookID>1234476</PublisherBookID> 58: <PublicationDate>2000-06-01</PublicationDate> 59: <Price>46. 95</Price> 60: </Book>
NOTE
Before you continue, understand that there are now five different values assigned to the BestSeller option: yes, no, impossible, guaranteed, and dud.
Reopen listing15-2.xsl and modify the <xsl:for-each> loop to match Listing 15.4. Save the updated file as listing15-4.xsl.
Listing 15.4 Using the XSL Elements to Create a Multiple Alternative Construct
1: <xsl:for-each select="Catalog/Book"
order-by="+Author/City">
2: <xsl:choose>
3: <xsl:when match=".[@BestSeller='yes']">
4: <tr>
5: <xsl:apply-templates/>
6: </tr>
7: </xsl:when>
8: <xsl:when match=".[@BestSeller='no']">
9: <tr style="font-weight:bold;color:red">
10: <td>Not a bestseller</td>
11: </tr>
12: </xsl:when>
13: <xsl:when match=".[@BestSeller='impossible']">
14: <tr style="font-weight:bold;color:red">
15: <td>It is impossible for this to be a
bestseller</td>
16: </tr>
17: </xsl:when>
18: <xsl:when match=".[@BestSeller='guaranteed']">
19: <tr style="font-weight:bold;color:red">
20: <td>Guaranteed to be a bestseller</td>
21: </tr>
22: </xsl:when>
23: <xsl:when match=".[@BestSeller='dud']">
24: <tr style="font-weight:bold;color:red">
25: <td>Definitely a dud</td>
26: </tr>
27: </xsl:when>
28: </xsl:choose>
29: </xsl: for-each>
Note that there's an xsl:when element for each of the possible values that the BestSeller attribute can have.
Reopen listing14-2.html and modify the lines that load the files so that listing15-3.xml is the XML file and listing15-4.xsl is the XSL file. The output when it's viewed in IE is shown in Figure 15.4.
){kind=link}
Figure 15.4 A different output for each possible value of the BestSeller attribute.
The following XSL element pair delimits a set of multiple alternatives written using the <xsl:when> and <xsl:otherwise> elements:
<xsl:choose> </xsl:choose>
There are five <xsl:when> elements in the construct, one for each of the possible values of the attribute:
<xsl:when match=".[@BestSeller='yes']">
<tr>
<xsl:apply-templates/>
</tr>
</xsl:when>
<xsl:when match=".[@BestSeller='no']">
<tr style="font-weight:bold;color:red">
<td>Not a bestseller</td>
</tr>
</xsl:when>
<xsl:when match=".[@BestSeller='impossible']">
<tr style="font-weight:bold;color:red">
<td>It is impossible for this to be a
bestseller</td>
</tr>
</xsl:when>
<xsl:when match=".[@BestSeller='guaranteed']">
<tr style="font-weight:bold;color:red">
<td>Guaranteed to be a bestseller</td>
</tr>
</xsl:when>
<xsl:when match=".[@BestSeller='dud']">
<tr style="font-weight:bold;color:red">
<td>Definitely a dud</td>
</tr>
</xsl: when>
In this case, the data is extracted only when the value of BestSeller is yes. For all other cases, a simple message is written to that row of the table.
An xsl:otherwise Example
As has already been mentioned, the other element used in association with <xsl:choose> is the <xsl:otherwise> element. It can be considered as the "none of the above" option.
Reopen listing15-4.xsl and modify it to match Listing 15.5. Save it as listing15-5.xsl.
Listing 15.5 Using the xsl:otherwise Element to Catch All Remaining Options
1: <xsl:for-each select="Catalog/Book"
order-by="+Author/City">
2: <xsl:choose>
3: <xsl:when match=".[@BestSeller='yes']">
4: <tr>
5: <xsl:apply-templates/>
6: </tr>
7: </xsl:when>
8: <xsl:when match=".[@BestSeller='no']">
9: <tr style="font-weight:bold;color:red">
10: <td>Not a bestseller</td>
11: </tr>
12: </xsl:when>
13: <xsl:when match=".[@BestSeller='impossible']">
14: <tr style="font-weight:bold;color:red">
15: <td>It is impossible for this to be a bestseller</td>
16: </tr>
17: </xsl:when>
18: <xsl:otherwise>
19: <tr style="font-weight:bold;color:red">
20: <td>Guaranteed to be a bestseller or a dud</td>
21: </tr>
22: </xsl:otherwise>
23: </xsl:choose>
24: </xsl: for-each>
Reopen listing14-2.html and modify the lines that load the files so that listing15-3.xml is the XML file and listing15-5.xsl is the XSL file. The output when it's viewed in IE is shown in Figure 15.5.
){kind=link}
Figure 15.5 Illustrating the xsl:otherwise element.
For the three values of yes, no, and impossible, there's an xsl:if element that will lead to specific actions. If the value of the BestSeller attribute is dud or guaranteed, the message in the xsl:otherwise option is displayed.