Shawndouglas: Created as needed.

2016-09-23T21:25:38Z

Created as needed.

New page

{{Documentation subpage}}
{{Lua|Module:If empty}}


This is the {{tl|If empty}} template.

*''Update 2014 Dec 23'': This template used to only take 9 parameters. This limit has been removed.

This template is used inside other templates. It takes any number of parameters and returns the first found to be defined and non-empty. If none is found, nothing is returned. Typical usage is like this:
: <code><nowiki>{{If empty |{{{logo|}}} |{{{image|}}} |{{{picture|}}} |default.svg}}</nowiki></code>
: <nowiki>("Return {{{logo|}}} if it has a value; else {{{image|}}} if it has a value; else {{{picture|}}} if it has a value; else return "default.svg".")</nowiki>
This returns the first of the parameters ''logo'', ''image'' and ''picture'' that is defined and non-empty, otherwise "default.svg".

===Rationale===
The MediaWiki parameter default function doesn't return the default value for empty parameters. That is, <code><nowiki>{{{logo|default.svg}}}</nowiki></code> does not return "default.svg" if the template was called like this: <code><nowiki>{{template|logo=}}</nowiki></code>.

The usual workaround for a single parameter is:
: <code><nowiki>{{#if:{{{logo|}}} |{{{logo}}} |default.svg}}</nowiki></code>
: <nowiki>("If {{{logo}}} has a value, return it, else return "default.svg".")</nowiki>

But this becomes complex when several parameters are to be checked:
: <code><nowiki>{{#if:{{{logo|}}} |{{{logo}}} |{{#if:{{{image|}}} |{{{image}}} |{{#if:{{{picture|}}} |{{{picture}}} |default.svg}} }} }}</nowiki></code>
: <nowiki>("If {{{logo}}} has a value, return it; else if {{{image}}} has a value, return that; else if {{{picture}}} has a value, return that; else return "default.svg".")</nowiki>
In these cases, {{tlf|if empty}} produces the simpler syntax (as above):
: <code><nowiki>{{if empty |{{{logo|}}} |{{{image|}}} |{{{picture|}}} |default.svg}}</nowiki></code>

====Piping====
Parameters used with {{tlf|if empty}} must be piped – i.e. include the vertical bar (pipe) symbol {{nowrap|("{{thin space}}|{{thin space}}")}} as a trailing character – so that empty or undefined parameters aren't treated as text and returned incorrectly. Hence, for example, <code><nowiki>{{{logo|}}}</nowiki></code>, <code><nowiki>{{{image|}}}</nowiki></code> and <code><nowiki>{{{picture|}}}</nowiki></code> rather than {{param|logo}}, {{param|image}} and {{param|picture}} in the above examples.

===Examples===
{{Aligned table |class=wikitable
|cols=3 |col1style=padding-right:1.0em; |col2style=padding-left:0.5em;padding-right:1.0em; |col3style=padding-left:0.5em;
|row1style=background:whitesmoke;padding-left:0.5em;font-weight:bold;
| Code | Result |
| {{tc|if empty}} | {{if empty}} | Returns an empty string.
| {{tc|if empty|one}} | {{if empty|one}} | Returns the first parameter that is defined and not empty.
| {{tc|if empty|one|two}} | {{if empty|one|two}} |
| {{tc|if empty|one|two|three|four}} | {{if empty|one|two|three|four}} |
| {{tc|if empty||two}} | {{if empty||two}} | The first parameter is empty/undefined, so is passed over.
| {{tc|if empty||two|three|four}} | {{if empty||two|three|four}} |
| {{tc|if empty||two||four}} | {{if empty||two||four}} |
| <code><nowiki>{{if empty||||||||||ten}}</nowiki></code> | {{if empty||||||||||ten}} | Unlike in previous versions, this template is no longer limited by 9 parameters.
| {{tc|if empty|}} | {{if empty|}} | The only parameter is empty or undefined, so returns an empty string.
| {{tc|if empty||||}} | {{if empty||||}} | Returns an empty string.
| <code><nowiki>{{if empty|{{{1|}}}|{{{2|}}}|three}}</nowiki></code> | {{if empty|{{{1|}}}|{{{2|}}}|three}} |
| <code><nowiki>{{if empty|{{{1}}}|{{{2}}}|three}}</nowiki></code> | {{if empty|{{{1}}}|{{{2}}}|three}} | No pipe-characters following the names of the first two parameters ("1" and "2"), so the first of these returned as text ("{{{1}}}").
| <code><nowiki>{{if empty|{{{logo|}}}|two}}</nowiki></code> | {{if empty|{{{logo|}}}|two}} |
| <code><nowiki>{{if empty|{{{logo}}}|two}}</nowiki></code> | {{if empty|{{{logo}}}|two}} | No pipe-character following the parameter name "logo", so the text "{{{logo}}}" returned.
| <code><nowiki>{{if empty|p=q}}</nowiki></code> | {{if empty|p=q}} | The template identifies the parameters it receives as parameters 1 to 9, not using names such as "p", etc.
}}

===See also===
* {{tl|if all}}
* {{tl|if either}}

<includeonly>{{#ifeq:{{SUBPAGENAME}}|sandbox |
| 
[[Category:If-then-else templates]]
}}</includeonly>

Template:If empty/doc - Revision history

Shawndouglas: Created as needed.