Template:If empty

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{{IfemptyTemplate:Ifempty}}
{{First nonemptyTemplate:First nonempty}}
{{Use first nonemptyTemplate:Use first nonempty}}

This template uses Lua:

Module:If empty

This template is used on 55,000+ pages and changes may be widely noticed. Test changes in the template's /sandbox or /testcases subpages, or in your own user subpage. Consider discussing changes on the talk page before implementing them.

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".

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

Code	Result
`{{if empty}}`		Returns an empty string.
`{{if empty\|one}}`	one	Returns the first parameter that is defined and not empty.
`{{if empty\|one\|two}}`	one
`{{if empty\|one\|two\|three\|four}}`	one
`{{if empty\|two}}`	two	The first parameter is empty/undefined, so is passed over.
`{{if empty\|two\|three\|four}}`	two
`{{if empty\|two\|four}}`	two
`{{if empty\|\|\|\|\|\|\|\|\|\|ten}}`	ten	Unlike in previous versions, this template is no longer limited by 9 parameters.
`{{if empty}}`		The only parameter is empty or undefined, so returns an empty string.
`{{if empty}}`		Returns an empty string.
`{{if empty\|{{{1\|}}}\|{{{2\|}}}\|three}}`	three
`{{if empty\|{{{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}}}").
`{{if empty\|{{{logo\|}}}\|two}}`	two
`{{if empty\|{{{logo}}}\|two}}`	{{{logo}}}	No pipe-character following the parameter name "logo", so the text "{{{logo}}}" returned.
`{{if empty\|p=q}}`		The template identifies the parameters it receives as parameters 1 to 9, not using names such as "p", etc.

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Template:If empty

Rationale

Piping

Examples

See also

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