Template:Ifdef
{{{2}}}
Documentation
{{ifdef}}
is a compact variant of {{Qif}} for simple
"if defined then do" statements
without else part. It's the opposite of {{ifndef}}.
Usage
{{Ifdef|value|result}}
yields result if value isn't blank.
This template is used to simplify the following equivalent but somewhat cryptic code variants:
{{{1{{{1|}}}|{{{2}}}}}}{{{value{{{value|}}}|{{{result}}}}}}{{{test{{{test|}}}|{{{then}}}}}}
Example
| Code | Result |
1 {{Ifdef| |empty}}
|
1 |
2 {{Ifdef|x|gotcha}}
|
2 gotcha |
3 {{Ifdef| {{{1| }}} | {{{1| }}} undefined}}
|
3 |
4 {{Ifdef| {{{1|x}}} | {{{1|x}}} for an u}}
|
4 x for an u |
5 {{Ifdef| {{{ 1 }}} | {{{1}}} bad idea}}
|
5 {{{1}}} bad idea |
6 {{Ifdef| {{!}} |see also {{Tl|Qif}} }}
|
6 see also {{Qif}}
|
7 {{Ifdef| okay | 2=see=[[#Caveats]] }}
|
7 see=#Caveats |
8 {{Ifdef| oops | see=[[#Caveats]] }}
|
8 {{{2}}} |
See also a simpler example using ifdef. There's no default in ifdef for the second parameter, because this could hide problematic code.
Caveats
In templates the characters "=" (=) and "|" (|) cannot be used as is in parameters. The numeric character references = and | are often good enough, but for Wiki and XHTML markup the literal characters are required:
- For | template:! (edit•talk•links•history) offers a workaround.
- For = the template parameter mechanism allows
{{ifdef}}resulting in "ok=yes" instead of{{ifdef}}resulting in "{{{2}}}".
Substitution works only for {{ifdef}}, but not for {{ifndef}} or {{qif}}.
See also
{{Ifdef}}{{Ifndef}}{{Qif}}- Parser functions #expr:, #if:, #ifeq:, etc.
Source
Copied from the page on meta where it is released under the GFDL.