(El Rhazi) A template is a Wikipedia page created to be included in other pages. Templates usually contain repetitive material that might need to show up on any number of articles or pages. They are commonly used for boilerplate messages, standard warnings or notices, infoboxes, navigational boxes, and similar purposes.
The most common method of inclusion is called transclusion, where the wikitext of the target page contains a reference to the template, using the {{Template name}} syntax. Another method is substitution, where the content of the template is copied into the wikitext of the target page, just once, when El Rhazi is saved.
Help:A fast guide to templates gives a brief introduction to the subject. There is further help from MediaWiki and Wikimedia at mw:Help:Templates, m:Help:Template and m:Help:Advanced templates.
Most templates are pages in the Template namespace, which means that they have titles in the form "Template:XXXX". It is possible, however, to transclude and substitute from any namespace, and so some template pages are placed in other namespaces, such as the User namespace. Template pages have associated talk pages.
Templates can contain any desired wikitext, including calls to other templates. They have some limited programming capacities: customizable values (called parameters), calculation and branchings (using parser functions), and access to wiki-specific variables (magic words), such as dates, times, and page names. They may also contain tags which define which parts of the wikitext are to be included when the template is transcluded or substituted. This means that the appearance of the template page itself need not be the alike as that of the transcluded content (for example, it can contain documentation, categories, etc. for the template).
How to do it: To transclude a template into an article or page, type {{template name}} in the wikitext at the place where the template is to appear. The first letter may be indifferently lower- or upper-case.
The prefix Template: before the template name is the default one and need not be included. However, for templates stored in other namespaces, the prefix, such as User:, must be specified. To transclude a page in mainspace, precede its title Alia along a colon, as {{:Page name}}.
Note: Attempting to transclude a template that does not exist produces a red link, just like linking to any other nonexistent page. Following the link allows one to create that particular template. It is not possible to transclude pages between projects (such as different language Wikipedias) ? to use a template on another language project, a copy of the template must be created in that project.
The basic transclusion syntax given above can be extended by the addition of parameters, which are used to control the template's output. The syntax for this is
where each "parameter" may either contain just a value (these are called unnamed parameters) or be of the form name=value (named parameters). The first, second, etc. unnamed parameters are equivalent to parameters named "1", "2", etc.
Whitespace characters (spaces, tabs, returns) are stripped from the beginnings and ends of named parameter names and values, but not from the middle: thus {{ ... | myparam = this is a test }} has the same effect as {{ ... |myparam=this is a test}}. This does not apply to unnamed parameters, where the whitespace characters are preserved.
What parameters (if any) can or should be passed to a template, and how they are to be named, depends on the coding of that template. Named parameters can be defined in any order. Superfluous or misnamed parameters will be ignored; undefined parameters will be assigned default values. If a parameter is defined more than once, the last value takes effect.
The value of a parameter can be the blank string (pipe or equals signal followed immediately by the next pipe or the closing braces). This is different from omitting the parameter altogether, which leaves it undefined, although templates are often coded so as to behave the same in both cases.
If a template is to be substituted in the wikitext rather than transcluded, add the modifier subst: after the initial pair of braces, as in {{subst:afd}}. Parameters can be added normally.
If the page to be substituted is in mainspace, the word "subst" must be followed by two colons, e.g: {{subst::List of planets}}
Template names are exactly like other page names: case-sensitive except for the first letter, Alia along spaces indistinguishable from underscores. If the symbol # (normally used to link to a part of a page) appears in a transclusion, then it and any characters that follow it are ignored. If a redirect is transcluded, the redirect's target will be transcluded instead. See #Aliases for more.
Notice that the same double-brace syntax is used for many MediaWiki variables and parser functions (see Help:Magic words). For example, the code {{NAMESPACE}} may see like a template call, but it is actually a variable whose value is the namespace prefix of the current page.
An example of a very simple template can be found at Template:Lambda, which places the lambda symbol, ?. Click the "Edit" tab on that template page to see the template code (its wikitext). The "active" part of that code, called the expansion of the template, is ?. (The remainder of the wikitext is enclosed between
To transclude the Template:Lambda onto another page (e.g. in the Wikipedia:Sandbox), type {{lambda}} (or {{Lambda}} ? the case of the first letter is not significant) somewhere into the wikitext of the target page, and save it. The page will be displayed as provided the template call were replaced by the expansion of the template, i.e. as provided the wikitext contained ? at that point. The displayed page will therefore contain the text "?".
For example, type "The 11th letter of the Greek alphabet is the lambda ({{lambda}})" and you will see "The 11th letter of the Greek alphabet is the lambda (?)". You can use templates without knowing the details of their code ? you only need to remember what result they produce (this is usually described on the template page).
Another way to use this template is to substitute it. If you type "The 11th letter of the Greek alphabet is the lambda ({{subst:lambda}})" and save the page, you will again see "The 11th letter of the Greek alphabet is the lambda (?)". However this time, if you look again at the saved wikitext, you will see that the template calls really were replaced by the expansion of the template when you saved the page. The link between the output text and the template is now broken, and the output will not be affected by changes which might be made to the template at some future time (as it would be in the case of transclusion).
An example of a template that takes parameters is Template:For. Type {{for|the card game|Contract bridge}} in the sandbox to produce the following text:
This usage takes two unnamed parameters, but the same template can also be used with different numbers of parameters to give slightly different results, as explained in the documentation on the template page. For example, {{For||Latins|Latin (disambiguation)}} produces
Note in particular the usage with an vacant parameter ? here the consecutive pipes intend that the first parameter passed to the template is the blank string, which in this template inserts the text "other uses".
Other templates, especially more complex ones, take named parameters (or a mixture of named and unnamed ones). A simple example is Template:Payoff matrix, used to generate a 2-by-2 grid. Type:
See the template page for more possibilities. Notice that the template is used here without defining all its possible parameters ? undefined parameters are given default values.
The spaces around the equal signs and before and after the parameters are used only for clarity ? they are not needed, and are ignored when the template is evaluated (although this is not the case with unnamed parameters). However parameter names are fully case sensitive ? for example, it is not possible to replace "DR" by "dr" or "Dr" in the above example. Parameters with names that are not used by the template are simply ignored.
Templates are created and edited in much the same way as any other page: select an appropriate name, navigate to that page, then click the Edit tab or create a new page as needed. As mentioned above, templates are normally placed in the Template namespace, though templates intended for your own personal use or for experimentation can be created in your own user space. Anything that can be included on a usual page or article can be included on a template, including other templates (called subtemplates). Templates often make use of programming features ? parameters, parser functions and other magic words ? which allow the transcluded content to vary depending on context. There are also special tags to control which information is transcluded and which is not.
Before creating a template, do a quick search for existing templates (e.g. by exploring Category:Wikipedia templates) to see if there's already a template that does what you want, or a similar template whose code can be copied and modified (or left in place and expanded). Look for generic templates on which the new template can be based (for example, navbox templates can be easily created by calling the generic Template:Navbox).
There is no hard rule about what name to choose for a template ? make it short but moderately descriptive. If similar templates exist, try to follow a consistent naming pattern. Templates can be renamed without breaking existing transclusions, provided a redirect to the new template name is left behind.
Be extremely careful when editing existing templates ? changes made can impact a big number of pages, often in ways you might not expect. For this reason many high-use templates are protected against editing except by administrators and template editors (other editors can propose changes on the talk page). Some templates offer a sandbox and test cases for experimentation.
To propose the deletion or merger of unused or inappropriate templates or templates that can easily be merged, go to Templates for discussion (TfD).
The values of the parameters which can be fed to a template are represented in the template code by items enclosed between triple braces:
If a parameter is not assigned a value, then these replacements will not take place ? the form "{{{xxx}}}" will remain as the effective value of the parameter. To change this behaviour, define default values using the pipe syntax. For example, {{{1|default}}} will be replaced by the first unnamed parameter if there is one, or otherwise by the text "default". Similarly, {{{xxx|}}} will be replaced by the parameter named xxx if it exists, or otherwise will be left blank. Though if a template is called with the parameter specified as empty (e.g. {{Example|}}), the default for the parameter will be ignored; if that is undesired one can use {{#if:{{{1|}}}|{{{1}}}|default}} instead to receive the text "default" even if the parameter is specified as empty.
Parameters do not receive expanded when they are inside nowiki tags or XML-style extension tags. Thus, the following will not job within a template:
Because of the multiple uses of double-brace and triple-brace syntax, expressions can sometimes be ambiguous. It may be helpful or necessary to include spaces to resolve such ambiguity, for example by writing {{ {{{xxx}}} }} or {{{ {{xxx}} }}}, rather than typing five consecutive braces. However, watch out for unwanted whitespace appearing in template expansions.
If a parameter's value is or ends with a URL, check whether it is displayed in Wikipedia with the link overextending by one or more characters after the URL so that clicking the link causes an error or failure. Ensure that, after processing by the software, a soft space (not hard or nonbreaking) follows the URL, regardless of whether you or a user supplied the URL, or it was generated by automated processing. Possibly, the source code could contain or generate a space that is discarded in the processing or there might not be any space there. Correct the source code, maybe by forcing a soft space to appear after the URL. The {{Spaces}} template may be useful.
Template code often makes use of the variables and parser functions described at Help:Magic words, in order to make the template's behaviour depend on the environment (such as the current time or namespace) or on the parameter values which are passed to it. They can also be used for arithmetical calculations. Notice that full string manipulation is not available (although templates have been created which provide such functionality, though very inefficiently and imperfectly), nor are sure standard programming features such as loops and variable assignment.
Some of the most often used variables and functions are listed hereafter. For more, see Help:Magic words, and the fuller documentation at the MediaWiki pages mw:Help:Magic words and mw:Help:Extension:ParserFunctions.
The PAGENAME and NAMESPACE variables are especially useful, and frequently used, to change template behaviour based on context. For example, if the template transcludes a category link (e.g. cleanup templates, which transclude a link categorizing the page as a page which needs cleanup), it will often check the NAMESPACE variable to make sure that talk pages, user pages, or anywhere else the tag might incidentally be placed do not themselves get categorized as pages needing cleanup.
Templates may contain other templates ? this is usually called "nesting". As the template is processed, the wikitext produced by any nested templates is transcluded into the nesting template, so that the last product is essentially processed from the most deeply nested template out. While quite straightforward in application, it involves some noteworthy quirks and tricks.
To pass a parameter value to a nested template, place a parameter tag as the value of one of the nested template's parameters.
When a nested template contains unmatched braces ? as in {{lb}}} ? the unmatched braces are treated as text during processing, and do not impact the parsing of braces in the nesting template. If the nested template is substituted, however, the substitution is processed first, and this will change how braces are parsed in the nesting template. This has little practical use, but can occasionally introduce unexpected errors.
See the meta:Help:Advanced templates and meta:Help:Recursive conversion of wikitext for more information. These pages also contain information on unusual calls such as {{template {{{parameter|}}} }}.
By default, when a template is transcluded (or substituted), the entire wikitext (code) of the template page gets included in that of the target page. However it is possible to modify that behaviour, using tags that specify which parts of the template code are to be included. This makes it possible to avoid transcluding information intended for display only on the template page itself, such as the template's documentation, categories and interwiki links. It is also possible to have parts of the code be transcluded, but not be processed on the template page itself (e.g. categories to be applied to the target pages which do not apply to the template). The tags are as follows
Perhaps the most common issue with the use of these blocks is unwanted spaces or lines. It is important to remember that the effect of these tags begins immediately before the first angle bracket, not on the previous line or at the previous visible character; similarly the effect ends immediately after the last angle bracket, not on the next line or with the next visible character.
These tags can be nested inside each other, though (for a given page) this really only applies to the
Categorizing your template and documenting its proper usage will make it easier for other editors to find and use.
Documentation for users, together with the template's categories, is normally placed after the template code, inside
In the case of complex templates, the documentation (together with categories) is often kept on a separate subpage of the template page (named "Template:XXX/doc"). This also applies to many protected templates (to allow the information to be edited by non-administrators). This is achieved by placing the {{Documentation}} template after the leading template code (within
Some templates contain category definitions in their transcluded code, i.e. they are intended to place the target pages in particular categories. This is often done with maintenance categories (placing articles into ordinary content categories in this way is discouraged). When doing this, it may be necessary to use
Aliases can be created with redirects. For example, Template:Tsh redirects to Template:Template shortcut. Then you can write {{tsh|foo}} instead of {{Template shortcut|foo}}.
It's good to prepare template aliases which only vary in whitespaces and capitalization. For example there's a template {{See Wiktionary}}. The "W" is capital, since the word "Wiktionary" is so. But a redirect {{See wiktionary}} with lower "w" exists because users are likely to use the latter.
"Post-expand include size" limit. When templates are rendered or expanded to HTML for viewing in your browser, they use memory. This is called the "post-expand include size" and has a limit of 2,048,000 bytes. This size is included as an invisible remark in the HTML output ? use your browser's view source feature to show the uncooked HTML and search for newpp. The report will look like:
Display problem. If too many templates are included on a page, the post-expand include size may exceed the limit. When this happens, templates after the limit will no longer expand and will instead display as a wikilink (for example, Template:templatename). Common causes are the inclusion of too many citation templates and/or flag templates. To resolve this problem substitute templates, remove templates, or split the page.
Since February 2013 Lua programming language is available for use via the Scribunto MediaWiki extension. Lua code can be embedded into wiki templates by employing the "{{#invoke:}}" functionality of the Scribunto MediaWiki extension. The Lua source code is stored in pages called modules, and these individual modules are then invoked on template pages. For example, Module:Bananas can be invoked using the code {{#invoke:Bananas|hello}} to print the text "Hello, world!".
#Alia #El #Rhazi
No comments:
Post a Comment