Difference between revisions of "Template:If empty"

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test>Anthony Appleyard
m (Anthony Appleyard moved page Template:Ifempty to Template:If empty: Requested at WP:RM as uncontroversial (permalink))
test>Jackmcbarn
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<includeonly>{{{{{|safesubst:}}}#if:{{{1|}}}
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<includeonly>{{#invoke:If empty|main}}</includeonly><noinclude>{{Documentation}}</noinclude>
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        | {{{5}}}
 
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          | {{{6}}}
 
          | {{{{{|safesubst:}}}#if:{{{7|}}}
 
            | {{{7}}}
 
            | {{{{{|safesubst:}}}#if:{{{8|}}}
 
              | {{{8}}}
 
              | {{{{{|safesubst:}}}#if:{{{9|}}}
 
                | {{{9}}}
 
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{{Documentation}}
 
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Revision as of 21:57, 23 December 2014

Template documentation[view] [edit] [history] [purge]

Template:Template redirect

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:

{{If empty |{{{logo|}}} |{{{image|}}} |{{{picture|}}} |default.svg}}
("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".")

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, {{{logo|default.svg}}} does not return "default.svg" if the template was called like this: {{template|logo=}}.

The usual workaround for a single parameter is:

{{#if:{{{logo|}}} |{{{logo}}} |default.svg}}
("If {{{logo}}} has a value, return it, else return "default.svg".")

But this becomes complex when several parameters are to be checked:

{{#if:{{{logo|}}} |{{{logo}}} |{{#if:{{{image|}}} |{{{image}}} |{{#if:{{{picture|}}} |{{{picture}}} |default.svg}} }} }}
("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".")

In these cases, {{if empty}} produces the simpler syntax (as above):

{{if empty |{{{logo|}}} |{{{image|}}} |{{{picture|}}} |default.svg}}

Piping

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

Examples

Script error: No such module "aligned table".

See also