Plantilla:If empty

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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 ("|") 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.

Exemples

Codi Resultat
{{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.