Template:If empty/doc
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This is the {{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:
-
{{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".
Contents
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 ("Template:Thinsp|Template:Thinsp") 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 Template:Param, Template:Param and Template:Param in the above examples.
Examples
{{safesubst:#invoke:aligned table|table}}
See also
- {{if all}}
- {{if either}}
- Help:Parameter default