帮助:Conditional tables

ParserFunctions allow for the conditional display of table rows, columns or cells (and really, just about anything else). But Parser functions have some limits.

Basic use

The following example shows a basic use for #if that is available from the extension ParserFunctions:

 {{#if:{{{variable_foo|}}}
 |foo is set to '''{{{variable_foo}}}'''
 |foo is ''blank''}}

Here, {{{variable_foo}}} is checked to see if it is defined with a non-blank value. The table below shows the output from a template call (we'll call the template {{Conditional tables/example 1}}) with different values for {{{variable_foo}}}:

Template call	Result
{{Conditional tables/example 1}}	模板:Conditional tables/example 1
{{Conditional tables/example 1|<variable_foo=>}}	模板:Conditional tables/example 1
{{Conditional tables/example 1|<variable_foo=value>}}	模板:Conditional tables/example 1

Positional parameters {{{1}}} etc. work like named parameters:

 {{#if:{{{1|}}}
 |1st parameter is '''{{{1}}}'''
 |1st parameter is ''blank''}}

Template call	Result
{{Conditional tables/example 1b|< |bar>}}	模板:Conditional tables/example 1b
{{Conditional tables/example 1b|<foo|bar>}}	模板:Conditional tables/example 1b
{{Conditional tables/example 1b|<[[m:|not empty]]>}}	模板:Conditional tables/example 1b
{{Conditional tables/example 1b|<bad=idea>}}	模板:Conditional tables/example 1b
{{Conditional tables/example 1b|<1=ok=yes>}}	模板:Conditional tables/example 1b

Note how the pipe symbol (vertical bar) in the link works as is, it's not quite that easy within Wiki tables, see below.

Hiding rows entirely

It's also possible to hide rows of data within a table, however, there are issues you should be aware of.

Incorrect usage

Unfortunately #if and the MediaWiki table syntax do not work together well. For example, the following, {{Conditional tables/example 2}} is invalid and will not work:

{| class="wikitable"
{{#if:{{{variable_foo|}}}
|
|-
! Foo
| {{{variable_foo}}}
}}
|-
! Bar
| {{{variable_bar}}}
|}

The table below demonstrates the effect when {{Conditional tables/example 2}} is used:

Template call	Result
{{Conditional tables/example 2}}	模板:Conditional tables/example 2
{{Conditional tables/example 2|variable_foo=}}	模板:Conditional tables/example 2
{{Conditional tables/example 2|variable_foo=|variable_bar=bar}}	模板:Conditional tables/example 2
{{Conditional tables/example 2|variable_foo=value}}	模板:Conditional tables/example 2
{{Conditional tables/example 2|variable_foo=value|variable_bar=bar}}	模板:Conditional tables/example 2

The problem is with the usage of the pipe character (|). This character, in template calls, is used to separate parameters and so is invalid.

Correct usage

Plan A

One method of hiding rows in tables (or other structures within tables) uses HTML directly. HTML is more complicated than MediaWiki table syntax, but not much more so. In general, there are only a handful of HTML tags you need to be aware of

• <tr> - this tag creates a new row (similar to |- in MediaWiki table syntax)
• <th> - this tag creates a new header cell within a row (similar to ! in MediaWiki table syntax)
• <td> - this tag creates a new cell within a row (similar to | in MediaWiki table syntax)
• <caption> - this tag creates a caption (similar to |+ in MediaWiki table syntax)

Working from the invalid template example above, by switching to HTML we end up with the following code:

{| class="wikitable"
{{#if:{{{variable_foo|}}}
|<tr><th>Foo</th><td>{{{variable_foo}}}</td></tr>}}
|-
! Bar
| {{{variable_bar}}}
|}

The code above is in {{Conditional tables/example 2a}}. As before, the table below demonstrates the effect when it's used:

Template call	Result
{{Conditional tables/example 2a}}	模板:Conditional tables/example 2a
{{Conditional tables/example 2a|variable_foo=}}	模板:Conditional tables/example 2a
{{Conditional tables/example 2a|variable_foo=|variable_bar=bar}}	模板:Conditional tables/example 2a
{{Conditional tables/example 2a|variable_foo=value}}	模板:Conditional tables/example 2a
{{Conditional tables/example 2a|variable_foo=value|variable_bar=bar}}	模板:Conditional tables/example 2a

Plan B

As noted above the only problem is the vertical bar or pipe symbol within a template. Often it's good enough to replace problematic characters by numeric references, e.g. "{" by {, "|" by |, and "}" by }. But for Wiki tables a real "|" delimiter is required — using | doesn't work as delimiter.

A simple trick allows to protect the "|" in template parameter values while still arriving as real "|" delimiter in the Wiki table, see the magic word {{!}}. Note that "!" (exclamation mark) has no problems with templates, it's the other delimiter used in Wiki tables. Here's the code for plan B:

{| class="wikitable"
{{#if:{{{foo|}}}|
{{!}}-
! Foo
{{!}} {{{foo}}}
}}
|-
! Bar
| {{{bar}}}
|}

The code above is in {{Conditional tables/example 2b}}. As before, the table below demonstrates the effect when it's used:

Template call	Result
{{Conditional tables/example 2b|<bar=nobar>}}	模板:Conditional tables/example 2b
{{Conditional tables/example 2b|<foo=>|<bar=vbar>}}	模板:Conditional tables/example 2b
{{Conditional tables/example 2b|<foo=value>}}	模板:Conditional tables/example 2b
{{Conditional tables/example 2b|<foo=value>|<bar=vbar>}}	模板:Conditional tables/example 2b

Plan C

Perhaps the simplest option is to use the conditional with the CSS "display: none" property as follows:

{| class="wikitable"
|- {{#if: {{{variable_foo|}}} | | style="display: none;" }}
! Foo
| {{{variable_foo}}}
|-
! Bar
| {{{variable_bar}}}
|}

In this way there is no need for the wikitables pipe character to appear in the #if conditional. However, sources and notes referred to in the muted cells won't get suppressed with the other contents, to the effect that they continue to be listed at the end of an article without any references to them occurring in the article's text. Also, this method only works with browsers supporting CSS.

The code above is in {{Conditional tables/example 2c}}. As before, the table below demonstrates the effect when it's used:

Template call	Result
{{Conditional tables/example 2c|<variable_bar=bar>}}	模板:Conditional tables/example 2c
{{Conditional tables/example 2c|<variable_foo=>|<variable_bar=bar>}}	模板:Conditional tables/example 2c
{{Conditional tables/example 2c|<variable_foo=foo>}}	模板:Conditional tables/example 2c
{{Conditional tables/example 2c|<variable_foo=foo>|<variable_bar=bar>}}	模板:Conditional tables/example 2c

Getting help

If you find yourself unable to get a template to behave how you like, you can try asking on Village pump, placing a request at Requested templates, or contacting an editor via IRC.

See also

For avoiding blank rows in the case of successive optional rows, see m:Help:Table.

For more information on #if (and other # functions), see:

• mw:Help:Extension:ParserFunctions

The following help topics deal with templates:

• m:Help:Template
• m:Help:Advanced templates

This help topic deals with table design (since most templates use tables, this may be useful):

• Help:Table

And finally:

• Help:Conditional expressions