الگو:اگر خالی/آزمایشی

توضیحات الگو[نمایش] [ویرایش] [تاریخچه] [پاکسازی]

الگو:Ifempty and الگو:Ifempty redirect here.

This is the {{if empty}} template.

This template is used inside other templates. It takes up to nine parameters (unnamed parameters 1-9) 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}}

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This returns the first of the parameters logo and image 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: {{الگو|logo=}}.

The usual workaround for a single parameter is:

{{#if:{{{logo|}}} |{{{logo}}} |default.svg}}

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But this becomes complex when several parameters are to be checked:

{{#if:{{{logo|}}} |{{{logo}}} |{{#if:{{{image|}}} |{{{image}}} |{{#if:{{{picture|}}} |{{{picture}}} |default.svg}} }} }}

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In these cases, {{if empty}} produces the simpler syntax (as above):

{{Ifempty|{{{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
{{Ifempty|||||||||nine}}	nine
{{Ifempty||||||||||ten}}		Empty string returned if maximum of nine parameters exceeded.
{{if empty|}}		The only parameter is empty or undefined, so returns an empty string.
{{if empty||||}}		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|2=x}}	x	Whether parameter 1 is undefined or empty does not matter.
{{Ifempty|p=q}}		The template identifies the parameters it receives as parameters 1 to 9, not using names such as "p", etc.

See also

• الگو:Tlspc
• الگو:Tlspc
• الگو:Tlspc assists in handling image-width parameters within templates.
• Help:Parameter default

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