Template:Ifempty/Documentation

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This is the {{Ifempty}} template.

This template is used inside other templates. It takes up to 9 parameters and returns the first found to be defined and non-empty. If none is found, nothing is returned. Typical usage is like this:

{{ifempty |{{{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, {{ifempty}} produces the simpler syntax (as above):

{{ifempty |{{{logo|}}} |{{{image|}}} |{{{picture|}}} |default.svg}}

Piping

Parameters used with {{ifempty}} 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

Code Result Notes
{{ifempty}} Returns an empty string.
{{ifempty|one}} one Returns the first parameter that is defined and not empty.
{{ifempty|one|two}} one
{{ifempty|one|two|three|four}} one
{{ifempty||two}} two The first parameter is empty/undefined, so is passed over.
{{ifempty||two|three|four}} two
{{ifempty||two||four}} two
{{ifempty||||||||||ten}} This template only supports 9 parameters.
{{ifempty|}} The only parameter is empty or undefined, so returns an empty string.
{{ifempty||||}} Returns an empty string.
{{ifempty|{{{1|}}}|{{{2|}}}|three}} three
{{ifempty|{{{1}}}|{{{2}}}|three}} {{{1}}} No pipe-characters following the names of the first two parameters ("1" and "2"), so the first of these returned as text ("{{{1}}}").
{{ifempty|{{{logo|}}}|two}} two
{{ifempty|{{{logo}}}|two}} {{{logo}}} No pipe-character following the parameter name "logo", so the text "{{{logo}}}" returned.
{{ifempty|p=q}} The template identifies the parameters it receives as parameters 1 to 9, not using names such as "p", etc.