Predloga:Ifempty/dok
To je dokumentacijska podstran za glavno stran Predloga:Ifempty. Namenjena je shranjevanju navodil, kategorizaciji in drugi vsebini, ki ni del glavne strani. Predloga ima preizkušanju namenjen peskovnik in testneprimere. |
Uporablja Lua: |
|
Predloga se uporablja na številnih straneh. Z urejanjem te predloge lahko zelo obremenite strežnike, zato pred uvedbo vse spremembe, ki jih želite uvesti, preizkusite na njenih podstraneh (/peskovnik oziroma /testniprimeri) ali na svojih lastnih podstraneh. Preizkusite jih lahko tudi v posebnem peskovniku za predloge. Preizkušene spremembe se lahko v predlogo dodajo z enim samim urejanjem. Preden predlogo spremenite, se o spremembah rajši pogovorite na njeni pogovorni strani. |
This is the {{If empty}} template.
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 and image that is defined and non-empty, otherwise "default.svg".
Rationale
urediThe 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
urediParameters 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
urediCode | Result | |
{{if empty}} | Returns an empty string. | |
{{if empty}} | one | Returns the first parameter that is defined and not empty. |
{{if empty}} | one | |
{{if empty}} | one | |
{{if empty}} | two | The first parameter is empty/undefined, so is passed over. |
{{if empty}} | two | |
{{if empty}} | 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. |
See also
uredi