RE: [xsl] Calling templates with (defaulted) params

["Michael Kay" <mhkay@xxxxxxxxxxxx>]

Specify <xsl:param name="x" value="default-value-here"/>

Mike Kay
Software AG

> -----Original Message-----
> From: owner-xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> [mailto:owner-xsl-list@xxxxxxxxxxxxxxxxxxxxxx]On Behalf Of Ruggier,
> Mario
> Sent: 31 May 2001 16:52
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject: [xsl] Calling templates with (defaulted) params
> 
> 
> Hi, 
> 
> in an XSLT that processes an XML description to produce HTML,
> I would like to be able to define any number of small "rendering"
> templates 
> for logical elements that I wish to define. To make the templates
> reusable,
> they are parametrized. The question is the number of parameters may be
> long, and having to state a value for each one each time the 
> template is
> called is not convenient. Is it possible to reduce overheaviness (i.e.
> not replace
> it by something just as heavy somewhere else in the code ;-) 
> by having 
> each template decide default values for each parameter, and uses it in
> each 
> case a parameter is not specified ?
> 
> In the small example below, imagine a logical "section", 
> represented by
> the <icm key="Section">, and a single param. This is processed by the 
> proposed XSLT, to call a template called "Section" that expects 2
> params.
> Imagine that the non-specified param should assume some value, 
> e.g. 'no value for note heading!'. Two ways of calling the template
> "Section"
> are included below, one with no defaults, and one with defaults, which
> is significantly heavier (and this is an example with only 2 params!).
> 
> My question is, are there other lighter ways to do this in XSLT?
> Any improvements anyone can suggest? 
> Any optimization should be in favour of many such templates, each 
> with possibly many parameters. And, any shortcuts should also favour
> the source xml description rather than the xsl that processes it.  
> 
> tia, and best regards, 
> 
> Mario Ruggier
> 
> 
> ==== xml source ====
> ...
> <icm key="Section">
>         <param name="heading" value="Section Heading" />
>         ....
> </icm>
> ...
> 
> 
> ===== xsl source ====
> 
> <xsl:output method="html" indent="yes" />
> 
> <!-- icm template wrapper to call templates according to @key 
> value -->
> <xsl:template match="icm">
>   <xsl:variable name="icm-key" select="@key" />
>   <xsl:choose>
>     ....
>     <xsl:when test="$icm-key='Section'">
> 
>       <!-- no defaulting... --> 
>       <xsl:call-template name="Section" >
>         <xsl:with-param name="heading"
> select="param[@name='heading']/@value" />
>         <xsl:with-param name="headingNote"
> select="param[@name='headingNote']/@value" />
>        </xsl:call-template>
> 
>       <!-- with defaulting... --> 
>       <xsl:call-template name="Section" >
>          <xsl:with-param name="heading">
>             <xsl:call-template name="get-defaulted-value">
>                 <xsl:with-param name="proposed-value"
> select="param[@name='heading']/@value" />
>                 <xsl:with-param name="default-value" select="'no value
> for heading!'" />
>             </xsl:call-template>
>          </xsl:with-param>
>          <xsl:with-param name="headingNote" 
>            <xsl:call-template name="get-defaulted-value">
>                 <xsl:with-param name="proposed-value"
> select="param[@name='headingNote']/@value" />
>                 <xsl:with-param name="default-value" select="'no value
> for heading note!'" />
>             </xsl:call-template>
>          </xsl:with-param>
>        </xsl:call-template>
> 
>     </xsl:when>
>     ...
>   </xsl:choose>
> </xsl:template>
> 
> ... <!-- other templates .--> 
> 
> <xsl:template name="Section" >
>   <xsl:param name="heading" />
>   <xsl:param name="headingNote" />
>     <table border="0" cellspacing="2" cellpadding="2" >
>       <tr valign="top" align="left">
>         <th bgcolor="#99ffff"><xsl:value-of select="$heading" /></th>
>         <td><xsl:value-of select="$headingNote" /></td>
>       </tr>
>       <xsl:apply-templates />
>     </table>
> </xsl:template>
> 
> ... 
> 
> <!-- "defaulting" function --> 
> <xsl:template name="get-defaulted-value">
>   <xsl:param name="proposed-value" />
>   <xsl:param name="default-value" />
>   <xsl:choose>
>     <xsl:when test="$proposed-value"><xsl:value-of
> select="$proposed-value" /></xsl:when>
>     <xsl:otherwise><xsl:value-of select="$default-value"
> /></xsl:otherwise>
>   </xsl:choose>
> </xsl:template>
> 
> 
> ========
> 
> 
> 
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> 

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