Help:Advanced templates

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This page is an extension of Help:Template. It concerns template names, variable names, and parameters depending on a variable or parameter. Note: This document refers to features currently only available in 1.6 and later.

Some described applications of these techniques may be outdated because often applying parser functions is better.

Contents

A template name or a parameter value depending on a parameter or variable

Both a template name and a parameter value can depend on a parameter or variable:

</body></html>"

  • {{ {{NAMESPACE}} }}, using Template:Help-meta containing "demonstration", gives "demonstration" (spaces needed)
  • see Template:Histogram

This allows branching depending on variables and parameters. However, using parser functions is more versatile.

Since with the method of this section no conditions such as {{{1}}}<a can be evaluated, and no substrings can be extracted from strings (not even currently with parser functions), etc., this works best if each parameter and variable has only a limited number of possible values. For example {{CURRENTDAYNAME}} has only seven possible values, so all cases can be handled with seven templates; if there are really only two cases, five of the seven could be redirects. On the other hand , {{CURRENTTIME}} has 1440 possible values, so it would be impractical to create a template or even just a redirect for each. Even with parser functions all the 1440 values have to be listed, see m:Template:hour (backlinks, edit) and m:Template:minute (backlinks, edit). An older method described below is another possibility, see e.g. m:Template:timedepcolor (backlinks, edit).

Having multiple parameters, which each can have only few values, is more flexible than having the same total number of possibilities in a single parameter.

If a template depends on PAGENAME, then the many possible values need not be a problem: only the pagenames of the pages that call the template apply, and these can be limited.

Branching according to {{{1}}}=a or {{{1}}}≠a is possible, see the section #A parameter name depending on a parameter.

Examples of pages that call a template with a name depending on a variable

  • NAMESPACE
  • PAGENAME
    • w:en:Template:H:f - for project-specific content on all help pages of the English Wikipedia (requires a blank template on all pages that no not have this content)

A variable name depending on a parameter

Example:

{{namespace|4}}, using Template:Namespace, containing

<includeonly><div id="RealTitleBanner"></includeonly>

{{selfref|1=The correct title of this article is '''<span id="RealTitle">{{{title|{{{1}}}}}}</span>'''. The article title conflicts with an existing [[Wikipedia:Namespace|namespace]] or [[Help:interwiki linking|interwiki prefix]]. }}</div><noinclude>


<center><big>'''IMPORTANT! THIS TEMPLATE SHOULD NEVER BE [[Wikipedia:Template substitution|SUBST'D]]!'''<big></center>

[[Category:Wrong title templates|{{PAGENAME}}]] </noinclude>

gives:

The correct title of this article is 4. The article title conflicts with an existing namespace or interwiki prefix.

A parameter name depending on a parameter

A parameter name in a template call (before "=") can depend on a parameter.

For example, using Template:t pnd containing "[[:Template:T pnd]]" with Template:t p containing "[[:Template:T p]]":

*{{t pnd|capital}}
*{{t pnd|country}}
*{{t pnd|something else}}

gives

  • Template:T pnd
  • Template:T pnd
  • Template:T pnd

This applies also for integer parameter names which normally do not require "=", but are now referred to by an expression on the left of "=".

Furthermore, multiple assignments of values to the same parameter in the same template call are allowed and result in the last value being used.

For example, {{t p|country=Belgium|capital=Paris|country=France}} gives "Template:T p".

The following is somewhat obsolete on wikis with the ParserFunctions extension, which allows easier branching.

This can be combined into the following branching technique:

{{tts|first parameter, with fixed name = name of template to be called if the parameter names are not equal | second parameter, with the name depending on parameters and/or variables = name of the template to be called if the parameter names are equal }} with Template:Tts containing {{{{{name of first parameter }}}}} (in this case that name is the empty string).

Thus, while carrying out an action in the case of equality can also be done simply by using a template name equal to the constant (the fixed name above), this technique also allows an action in the case of inequality, without having to cover all alternative values (different from the constant) separately.

Example:

Branching depending on whether a parameter is empty is illustrated with Template:T pdc containing "[[:Template:T pdc]]".

  • {{t pdc|abc}} gives Template:T pdc
  • {{t pdc|}} gives Template:T pdc

Unfortunately there is no control over the result when the parameter is undefined (as opposed to empty):

  • {{t pdc}} gives Template:T pdc

Example with an extra parameter:

Consider Template:ine containing "{{call|={{{1}}}|{{{2}}}=Nothing|1={{{2}}}|2={{{3}}}|3={{{4}}}}}", which calls Template:call containing "{{{{{}}}|{{{1}}}|{{{2}}}|{{{3}}}}}": If the first parameter is Not Empty then do the task given by the first parameter with the second, third and fourth parameter as its parameters, else do nothing; if the number of parameters of the task is 0, 1, or 2, ignore the superfluous values.

Using Template:Death containing "{{Navbox |name = Death |title = [[Death]] and related topics |groupstyle = line-height:1.1em; padding:0.35em 1em; |liststyle = line-height:1.4em;

|group1 = In medicine |list1 = {{nowrap begin}} [[Autopsy]]{{·w}} [[Brain death]]{{·w}} [[Clinical death]]{{·w}} [[Euthanasia]]{{·w}} [[Persistent vegetative state]]{{·w}} [[Terminal illness]]

|group2 = [[:Category:Death-related lists|Lists]] |list2 = {{nowrap begin}} [[List of causes of death by rate|Causes of death by rate]]{{·w}} [[Lists of people by cause of death|People by cause of death]]{{·w}} [[Deaths in 2007|Notable deaths in 2007]]{{·w}} [[Deaths in 2008|Notable deaths in 2008]] {{nowrap end}}

|group3 = Mortality |list3 = {{nowrap begin}} [[Immortality]]{{·w}} [[Infant mortality]]{{·w}} [[Legal death]]{{·w}} [[Maternal death]]{{·w}} [[Mortality rate]] {{nowrap end}}

|group4 = After death |list4 = {{nowrap begin}} [[Afterlife]]{{·w}} [[Burial]]{{·w}} [[Cremation]]{{·w}} [[Decomposition]]{{·w}} [[Funeral]]{{·w}} [[Grief]]{{·w}} [[Mourning]]{{·w}} [[Promession]]{{·w}} [[Resomation]]{{·w}} [[Séance]]{{·w}} [[:Category:Death customs|Customs]] {{·w}} [[Intermediate state]]{{·w}} [[Last Judgment]] {{nowrap end}}

|group5 = Research |list5 = {{nowrap begin}} [[Cryonics]]{{·w}} [[Out-of-body experience]] {{·w}} [[Near-death experience]] {{·w}} [[Lazarus phenomenon]] {{·w}} [[Near-death studies]]{{·w}} [[Reincarnation research]] {{nowrap end}}

|group6 = Other |list6 = {{nowrap begin}} [[Murder]] {{·w}} [[Genocide|Race-murder]]{{·w}} [[Self-murder]]{{·w}} [[Fascination with death]]{{·w}} [[Martyr|Martyrdom]]{{·w}} [[Sacrifice]]s&nbsp;([[Human sacrifice|Human]]{{·w}} [[Animal sacrifice|Animal]]){{·w}} [[War]]{{·w}} [[Death (personification)|Personification of Death]]{{·w}} [[Death and culture]]{{·w}} [[:Category:Death by country|Death by country]] {{nowrap end}} }}<noinclude>

[[Category:Biology navigational boxes|Death]] [[Category:Social science and society navbox templates|Death]]<!--probably needs focusing--> [[Category:Death|τ]] [[tr:Şablon:Ölüm]] </noinclude>":

  • {{ine|death|[[November 2]], [[2004]]|[[Amsterdam]]|}} gives:

"

v • d • e
Death and related topics
In medicine
Lists
Mortality
After death
Research
Other

".

  • {{ine|death||comment|}} gives "

    California Radio Markets: Bakersfield • Chico • Fresno • Los Angeles • Merced • Modesto • Oxnard-Ventura • Palm Springs • Redding • Riverside-San Bernardino • Sacramento • San Diego • San Francisco • San Jose • San Luis Obispo • Santa Barbara • Santa Cruz • Santa Maria-Lompoc • Santa Rosa • Stockton • Victor Valley • Visalia-Tulare-Hanford

    Other California Radio Regions: Crescent City • High Desert/Eastern Sierra • Eureka • Fort Bragg-Ukiah • Imperial Valley • Red Bluff • Susanville/Sierra Nevada • Yreka

    See also: List of radio stations in California
    v • d • e
    Radio stations in the High Desert/Eastern Sierra area (Arbitron #unranked) (R&R info)
    By FM frequency
    87.7¹ · 88.1 · 88.5 · 89.7 · 90.9 · 91.1 · 91.3 · 91.9 · 92.7 · 93.5 · 95.1 · 95.9 · 96.7 · 96.9 · 97.7 · 100.1 · 100.9 · 101.5 · 102.5 · 102.7 · 103.1 · 103.7 · 103.9 · 104.5 · 104.5 · 104.9 · 105.3 · 105.5 · 106.3 · 106.9
    By AM frequency
    610 · 1140 · 1220 · 1230 · 1240 · 1310 · 1340 · 1360 · 1380 · 1470 ·
    By callsign
    K61AJ¹ · KAVL · KBTW · KCEL · KCNQ · KCRY · KFRJ · KFXM · KGBB · KGBM · KGMX · KHDR · KHTS · KIQQ · KIQQ-FM · KKZQ · KLKX · KLOA (AM) · KLOA-FM · KNYE · KPTG-LP · KQAB · KRAJ · KRSX-FM · KSRY · KSSI · KSZL · KTPI · KTPI-FM · KUTY · KVLI-FM · KVVS · KWDJ · KWJL · KWTD · KWTH · KWTM · KWTW · KXXZ · KZIQ ·
    ".

    This can be useful inside another template, to avoid the texts "Date of death:" and "place of death:" for a living person.

    Also, without a separate template Death, with just the more general Template:p2p1p3 containing "[[:Template:P2p1p3]]":

    • {{ine|p2p1p3|[[November 2]], [[2004]]|Date of death:  |, place of death: [[Amsterdam]]}} gives:

    "Template:P2p1p3".

    This would not be convenient to use in many template tags, but could be used in an infobox in the form

    • {{ine|p2p1p3|{{{1}}}|Date of death:  |, place of death: {{{2}}}}}

    We can apply "subst" to remove a "template layer" for server efficiency. It makes no difference for the editors of the pages that include the infobox, and no difference for the editor who wants to understand all inner workings, but it is more cryptic for the editor of the infobox who wants to use template Ine as black box, without being confronted with the internal coding. It gives:

    • {{call|=p2p1p3|{{{1}}}=x0|1={{{1}}}|2=Date of death:  |3=, place of death: {{{2}}}}}

    Applying "subst" again is not possible for the general case where the first parameter may or may not be empty. It would have to be done separately for both cases, thus removing the branching capability.

    (Alternatively a separate parameter "dead" with one of the values "dead" and "alive" is used, see e.g. w:en:Template:Infobox President with the auxiliary templates w:en:Template:Infobox President/dead and the empty w:en:Template:Infobox President/alive. A disadvantage is the extra parameter: it has to be specified that a president is alive, it is not sufficient to leave the date of death empty, or that a president is dead, even if a date of death has been specified. An advantage is that backlinks are available, providing not only a list of dead, but also a list of alive presidents for which the infobox is used.)

    Similarly, where a table row dealing with a parameter is removed if the parameter is empty:

    w:en:Template:If defined call1 calls w:en:Template:Template_call1 with 1={{{2}}} followed by 1{{{1}}}=void; if {{{1}}} is empty then this overwrites the value of 1, so 1=void, otherwise 1={{{2}}}, giving an empty result or {{{{{2}}}|{{{3}}}}}. {{{3}}} is typically the same as {{{1}}} (at least that is the case in all five cases in w:en:Template:Infobox CVG). It avoids e.g. the text "Designer:" if the parameter {{{designer}}} is empty.

    More generally, using Template:If equal g containing "[[:Template:If equal g]]":

    • {{if equal g|x2|x3|{{NAMESPACE}}|Help|a||}} gives Template:If equal g
    • {{if equal g|x2|x3|Help|{{NAMESPACE}}|a||}} gives Template:If equal g
    • {{if equal g|x2|x3|{{NAMESPACE}}|Template_talk|a||}} gives Template:If equal g
    • {{if equal g|x2|x3|Template_talk|{{NAMESPACE}}|a||}} gives Template:If equal g

    Note that {{NAMESPACE}} produces underscores for spaces, which are not considered equal by the template:

    • {{if equal g|x2|x3|Template_talk|Template talk|a||}} gives Template:If equal g
    • {{if equal g|x2|x3|Template_talk|Template_talk|a||}} gives Template:If equal g

    A parameter name in a parameter tag can now depend on a parameter, see Template:T pnd1 and its talk page.

    Also a parameter name in a template call can now depend on a variable: {{ns:2}} gives User and {{PUser|User=abc}} gives Template:PUser, hence {{PUser|{{ns:2}}=abc}} gives Template:PUser

    Using "subst:" with manual recursion gives a stepwise replacement, useful for analyzing and explaining the working of templates calling other templates. See e.g. Template talk:Lop.

    Including the content of a template in a template or variable name or parameter value

    It is now possible to use a template with a name dependent on the content of another template. For example: {{{{tctc}} }}, using Template:Tctc containing "[[:Template:Tctc]]" and Template:Tc containing "<noinclude> This template is used in various tutorial pages and should not be altered; it should say 'in' and nothing else.

    [[Category:Demo template]] </noinclude>in", gives "{{Template:Tctc }}". If there are no parameters, a space is needed between e.g. the two pairs of closing braces.

    It is now possible (since about 19 October 2005) to use a variable with a name dependent on the content of a template.

    For example: {{CURRENT{{t day}}}} using Template:T day containing "[[:Template:T day]]" gives the text {{CURRENTTemplate:T day}}, which is indeed the value of {{CURRENTDAY}}

    It is now possible (since about 19 October 2005) to include the content of another template in a parameter value

    Examples:

    If you defined parameters such as {{Template sandbox|First|Second|name="Named"}}:

    First
    in
    Second
    {{{2}}}
    Name
    {{{name}}}

    .

    • {{x3|{{x5|{{tc}}}}}} gives

    If you defined parameters such as {{Template sandbox|First|Second|name="Named"}}:

    First

    If you defined parameters such as {{Template sandbox|First|Second|name="Named"}}:

    First
    in
    Second
    {{{2}}}
    Name
    {{{name}}}
    Second
    {{{2}}}
    Name
    {{{name}}}

    .

    Thus it is now also possible to use a data array as parameter of a template, e.g.:

    {{hist5a|x|t data}} using

    Template:Timcnl and

    Template:t data containing "[[:Template:T data]]" gives:

    Template:Hist5a

    A template containing an assignment of a parameter value to a parameter name

    With m:Template:t (backlinks, edit),

    • Template:t par ass 1 containing "[[:Template:T par ass 1]]"
    • Template:t par ass 2 containing "[[:Template:T par ass 2]]"
    • Template:t par ass 3 containing "[[:Template:T par ass 3]]"
    • {{t|{{t par ass 1}}}} gives start-Template:T par ass 1-end

    </body></html>

    • {{t|{{t par ass 2}}}} gives start-Template:T par ass 2-end

    </body></html>

    • {{t|{{t par ass 3}}}} gives start-Template:T par ass 3-end

    </body></html>

    The third example shows that a template cannot contain multiple assignments of a parameter value to a parameter name.

    Illustration of the possibilities of template calls and links

    [[aTemplate:T complexb|pTemplate:T complexq]]

    is the result of [[a{{t complex|c=d|g=h|k=m}}b|p{{t complex|c=d|g=h|k=n}}q]]

    where Template:T complex contains:

    [[:Template:T complex]]

    and Template:T aHelpbdd contains:

    [[:Template:T aHelpbdd]]

    [[w:en:{{n en|de}}]] gives [[w:en:Template:N en]].

    [[{{n en|de}} TV coverage of Wikipedia]] gives [[Template:N en TV coverage of Wikipedia]].

    This page can now also be included based on the code "de" using {{:{{n en|de}} TV coverage of Wikipedia}}.


    Producing the value of a parameter whose name depends on the value of another parameter

    A parameter value can be used as the name of another parameter, even of the same template. For example,

    {{tvv | parameter=foo | foo=bar}}

    using Template:tvv containing "[[:Template:Tvv]]" gives Template:Tvv.

    For different names the order of the parameters does not matter:

    {{tvv | foo=bar | parameter=foo }}

    still gives Template:Tvv.

    {{tvv|parameter={{{a|foo}}}|foo=bar}} gives Template:Tvv

    However, with substitution it gives the wikitext {{{{{{a|foo}}}}}} rendered as {{{foo}}} .

    Also, the technique cannot be applied multiple times. For example,

    {{tvvv | 1=foo | foo=bar | bar=biz}}

    using Template:tvvv containing "[[:Template:Tvvv]]" gives Template:Tvvv.

    This is e.g. applied in en:Template:Reg polyhedra db (backlinks, edit), which contains a 2D array in the form {{{{{1}}}|{{{2}}}|1-1=a11|..|m-n=amn}}. The first parameter is the name of a template that provides a particular selection and presentation of a selected row of the array, e.g. en:Template:Reg polyhedron stat table (backlinks, edit), the second parameter (which is the first parameter of the latter template) specifies the row. The latter templates references element j of the row concerned by a tag of the form {{{{{{1}}}-j}}}

    The technique can also be used to create control flow structures. An ifdef-function as in m:Template:ifdef (backlinks, edit) could look like:

    {{{test{{{test|}}}|{{{then}}}}}}

    If test is empty, we expand the empty test parameter, but if it contains data, then after trying to expand a non-existing testdata-parameter, we get the then-parameter value instead. Or a literal {{{then}}}, if there's intentionally no default value for then, and then is undefined - a crude mechanism to catch errors.

    Of course this fails for a say test value it if testit is defined. An example with numerical parameters:

    {{{1{{{1|}}}|okay}}}

    For a defined first parameter we expect to get the text okay. But if the value of the first parameter is say 0, and a tenth parameter exists, we get its value {{{10}}} instead of okay.

    It's slightly different for an ifndef-function as in m:Template:ifndef (backlinks, edit):

    {{{then{{{test|}}}|}}}

    If test is empty, then we expand the then parameter. But if test contains data, then we try to expand a nonexisting thendata-parameter, finally arriving at its empty default value (= after the second "|" pipe symbol).

    Again this fails if the non-existing parameter in fact does exist, e.g. for

    {{{x{{{1|}}}|}}}

    with a defined value y for x we expect to get the empty default for a non-existing xy. This fails if {{{xy}}} is defined and non-empty.

    An if-then-else could be a combination of those two, as in Template:if containing "{{{{{subst|}}}p{{{{{subst|}}}#ifeq:{{{1}}}|eq|1|2}}|{{{{{subst|}}}p{{{{{subst|}}}#ifeq:{{{2}}}|{{{3}}}|1|2}}|{{{4|}}}|{{{5}}}}}|{{{{{subst|}}}p{{{{{subst|}}}#if{{{1}}}:{{{2}}}|1|2}}|{{{3}}}|{{{4|}}}}}}}<noinclude>{{documentation}}</noinclude>".

    For simple ifdef-cases the best solution is arguably to use it without additional template, e.g. for text relevant only if the third positional parameter is defined use:

    {{{3{{{3|}}}|found third parameter}}}

    For the opposite ifndef-case there's unfortunately no similar direct approach. Substitution works for ifdef, but not ifndef or if.

    A parameter value can also be used as part of the name of another parameter:

    {{switch
  |{{CURRENTDOW}}
  |case: 1=Mon
  |case: 2=Tue
  |case: 3=Wed
  |case: 4=Thu
  |case: 5=Fri
  |case: 6=Sat
  |case: 0=Sun
  |default=No date
}}

    using Template:switch containing "{{{case: {{{1|}}}|{{{default|}}}}}}<noinclude> {{Tdeprecated|Switch|new=[[m:ParserFunctions|ParserFunctions]]}}

    <!--[[Category:If templates|Switch]]--> [[ar:قالب:اختيار]] [[br:Patrom:Hervez]] [[ca:Plantilla:Depenent]] [[pt:Predefinição:Switch]] [[sr:Шаблон:Switch]] [[sv:Mall:Switch]] [[vi:Tiêu bản:Switch]] </noinclude>" gives Wed

    Using this technique and an auxiliary template, we can produce a function that checks if two parameter values are the same:

    Template:equal containing "=<noinclude> {{pp-template|small=yes}} {{documentation}} </noinclude>", with Template:vv2 containing "[[:Template:Vv2]]".

    It will return 1 if equal, or null (the empty string) if not.

    See also


    edit

    Wikipedia-specific help

    None available.

    This page is a copy of the master help page at Meta (for general help information all Wikimedia projects can use), with two Wikipedia-specific templates inserted. To update the main text, edit the master help page for all projects at m:Help:Advanced templates. For Wikipedia-specific issues, use Template:Ph:Advanced templates (the extra text at the bottom of this page) or Template:Phh:Advanced templates for a Wikipedia-specific lead (text appears at the top of this page). You are welcome to replace the full wikitext of this page with that of the master page at Meta at any time. To view this page in other languages see the master page at Meta.