Plantilla:If empty/ús

Aquesta és la plantilla {{If empty}}.

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

Aquesta plantilla s'utilitza dins d'altres plantilles. Es necessita qualsevol nombre de paràmetres i retorna el primer dels paràmetres que estigui definit (que tingui un valor i, per tant, no buit). Si no en troba cap, no retorna res. L'ús típic és com aquest:

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

("Retorna {{{logo|}}} si té un valor; altrament {{{image|}}} si té un valor; altrament {{{picture|}}} si té un valor; altrament retorna "default.svg".")

Retorna el primer dels paràmetres logo, image i picture que estigui defininit i no buit, en cas contrari "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 ("Plantilla:Thinsp|Plantilla: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 Plantilla:Param, Plantilla:Param and Plantilla:Param in the above examples.

Exemples

Codi	Resultat
Plantilla:Tlc		Returns an empty string.
Plantilla:Tlc	one	Returns the first parameter that is defined and not empty.
Plantilla:Tlc	one
Plantilla:Tlc	one
Plantilla:Tlc	two	The first parameter is empty/undefined, so is passed over.
Plantilla:Tlc	two
Plantilla:Tlc	two
{{if empty||||||||||ten}}	ten	Unlike in previous versions, this template is no longer limited by 9 parameters.
Plantilla:Tlc		The only parameter is empty or undefined, so returns an empty string.
Plantilla:Tlc		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.

Vegeu també

• {{if all}}
• {{if either}}
• Help:Parameter default