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维基媒体模板 来自维基百科,自由的百科全书
此Template被引用於約610,000個頁面,佔全部頁面的8%。 為了避免造成大規模的影響,所有對此Template的編輯應先於沙盒、測試樣例或您的沙盒上測試。 測試後無誤的版本可以一次性地加入此Template中,但是修改前請務必於討論頁發起討論。 模板引用數量會自動更新。 |
此模板使用Lua语言: |
這是{{If empty}}模板。
此模板用於其他模板內。此模板將讀取任何參數並將第一個有參數的定義輸出。如果並無發現,不作輸出。典型用法如下:
{{If empty |{{{logo|}}} |{{{image|}}} |{{{picture|}}} |default.svg}}
This returns the first of the parameters logo, image and picture that is defined and non-empty, otherwise "default.svg".
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}}
But this becomes complex when several parameters are to be checked:
{{#if:{{{logo|}}} |{{{logo}}} |{{#if:{{{image|}}} |{{{image}}} |{{#if:{{{picture|}}} |{{{picture}}} |default.svg}} }} }}
In these cases, {{if empty}} produces the simpler syntax (as above):
{{if empty |{{{logo|}}} |{{{image|}}} |{{{picture|}}} |default.svg}}
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.
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 | |
{{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. |
上述文档嵌入自Template:If empty/doc。 (编辑 | 历史) 编者可以在本模板的沙盒 (编辑 | 差异)和测试样例 (编辑)页面进行实验。 请在/doc子页面中添加分类。本模板的子页面。 |
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