Help:Array

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Template:Phh:Array Note: The techniques covered in this article depend on features unavailable before MediaWiki 1.6. This pages explains various methods of creating a kind of associative array using templates.

Note that producing an array element for a given index value corresponds to a case statement or switch.

Contents

Function #switch

The function #switch provides the main array technique. Where this extension is available, the other methods are probably obsolete.

  • {{#switch:3|1=Mon|2=Tue|3=Wed|4=Thu|5=Fri|6=Sat|7=Son|undefined}} gives Wed
  • {{#switch:5|1=Mon|2=Tue|3=Wed|4=Thu|5=Fri|6=Sat|7=Son|undefined}} gives Fri
  • {{#switch:0|1=Mon|2=Tue|3=Wed|4=Thu|5=Fri|6=Sat|7=Son|undefined}} gives undefined

Using Template:Short DOW with switch (talk, backlinks, edit) containing "[[:Template:Short DOW with switch]]":

  • {{Short DOW with switch|3}} gives Template:Short DOW with switch
  • {{Short DOW with switch|5}} gives Template:Short DOW with switch
  • {{Short DOW with switch|0}} gives Template:Short DOW with switch

Put "#default=" in front of the default value if it contains "=":

  • {{#switch:advanced|simple=1+1=2|#default=999+999=1998}} gives 999+999=1998

Array technique using parameter defaults

m:Template:Short DOW par def (talk, backlinks, edit), based on parameter defaults, contains (without the newlines):

{{{if{{{1|u}}}|Mon}}}
{{{if{{{2|u}}}|Tue}}}
{{{if{{{3|u}}}|Wed}}}
{{{if{{{4|u}}}|Thu}}}
{{{if{{{5|u}}}|Fri}}}
{{{if{{{6|u}}}|Sat}}}
{{{if{{{0|u}}}|Son}}}

{{short DOW par def|ifu=|3=}} gives Template:Short DOW par def

{{short DOW par def|ifu=|6=|3=|5=|3=}} gives Template:Short DOW par def

The results are in the index order according to the template content, not in the order of the parameters in the template call. Multiple occurrences are removed.

See also m:Template:m to ft par def (talk, backlinks, edit).

Array technique using CSS

Unlike other methods, this method works only for final display, and only on modern browsers with enabled support for CSS. The result cannot be used in expressions for template names, parameter names, parameter values, page names in links, etc.

Example:

m:Template:Short DOW css d (talk, backlinks, edit) contains (without the newlines):

<span style="display:non{{{1|e}}}">Mon</span>
<span style="display:non{{{2|e}}}">Tue</span>
<span style="display:non{{{3|e}}}">Wed</span>
<span style="display:non{{{4|e}}}">Thu</span>
<span style="display:non{{{5|e}}}">Fri</span>
<span style="display:non{{{6|e}}}">Sat</span>
<span style="display:non{{{0|e}}}">Sun</span>
<tt>{{short DOW css d|3=}}</tt> gives Template:Short DOW css d
<tt>{{short DOW css d|6=|3=|5=|3=}}</tt> gives Template:Short DOW css d
Without CSS support the result is MonTueWedThuFriSatSun

Again, the results are in the index order according to the template content, not in the order of the parameters in the template call. Multiple occurrences are removed. A variant of this method uses the common.css class hiddenStructure, example:

m:Template:Short DOW css (talk, backlinks, edit) contains (without the newlines):

<span class="hiddenStructur{{{1|e}}}">Mon</span>
<span class="hiddenStructur{{{2|e}}}">Tue</span>
<span class="hiddenStructur{{{3|e}}}">Wed</span>
<span class="hiddenStructur{{{4|e}}}">Thu</span>
<span class="hiddenStructur{{{5|e}}}">Fri</span>
<span class="hiddenStructur{{{6|e}}}">Sat</span>
<span class="hiddenStructur{{{0|e}}}">Sun</span>
<tt>{{short DOW css|3=}}</tt> gives Template:Short DOW css
<tt>{{short DOW css|6=|3=|5=|3=}}</tt> gives Template:Short DOW css
Without CSS support the result is MonTueWedThuFriSatSun

Comparison of the CSS method and the parameter default method

Comparing the CSS method and the parameter default method, we see that each of the lines

<span style="display:non{{{3|e}}}">Wed</span>
<span class="hiddenStructur{{{3|e}}}">Wed</span>
{{{if{{{3|u}}}|Wed}}}

in a template T, called with

{{T|3=}}
{{T|3=}}
{{T|ifu=|3=}}

respectively, give Wed, and the empty string if 3 is left undefined.

Thus the parameter default method has similar functionality, but requires an extra parameter. It has the advantage that the result can be used in expressions for template names, parameter names, parameter values, page names in links, etc.

For comparison, suppose we would use the shorter word "ifu" instead of "HiddenStructure" (note that this would require that class "if" is undefined); then the lines are:

<span style="display:non{{{3|e}}}">Wed</span>
<span class="if{{{3|u}}}">Wed</span>
{{{          if{{{3|u}}}| Wed}}}

In the third method the wikitext in the template is 15 characters shorter than the second method, for each optional item, but each call is 5 characters longer.

In the second method conflicts with other class names have to be avoided, in the third method conflicts with other parameter names. The first method is best in this regard.

Array technique using a small auxiliary template

Example:

{{array
 |index=index
 |1=Mon
 |2=Tue
 |3=Wed
 |4=Thu
 |5=Fri
 |6=Sat
 |0=Sun
}}

using m:Template:array (talk, backlinks, edit), containing {{{{{{index}}}|{{{default|}}}}}}.

In the case of a constant index this can be useful for selection from predetermined options by a small edit. Alternatively index can be an expression depending on a variable, or, if the text is in a template, on a parameter.

Note that if only one template is used, the difference with the method above is that the array data are outside the template: they are provided in the template call.

Example where the text is in another template (with also a default value): m:Template:short DOW (talk, backlinks, edit), containing:

{{array
  |index={{{1}}}
  |1=Mon
  |2=Tue
  |3=Wed
  |4=Thu
  |5=Fri
  |6=Sat
  |0=Sun
  |default={{{1}}} is not a valid weekday number.
}}

Examples:

{{Short DOW|3}} gives Template:Short DOW

{{Short DOW|{{CURRENTDOW}}}} gives Template:Short DOW

{{Short DOW|7}} gives Template:Short DOW


Another version of the two templates could use a term other than "index", e.g. the empty string. However, it should be a term that itself is not used as array index:

{{t Short DOW|3}} using m:Template:t Short DOW (talk, backlinks, edit), containing:

{{array
  |{{{1}}}
  |1=Mon
  |2=Tue
  |3=Wed
  |4=Thu
  |5=Fri
  |6=Sat
  |0=Sun
  |default={{{1}}} is not a valid weekday number.
}}

(hence using implicit name "1" instead of "index") gives "Template:T Short DOW". The implicit 1=3 is overwritten by "1=Mon", and {{{Mon}}} would be produced; since it is undefined, the default is produced, with in this case a confusing error message: not the input is incorrect, but the template itself.

See also en:Template:switch (talk, backlinks, edit), where parameter names consist of "case: ", followed by the index.

For

m:Template:for (talk, backlinks, edit) allows not only to produce one array element, like above, but also more.

Examples:

{{for|call=Short DOW|3}} gives "

For 3, see Array (disambiguation)."

{{for|call=Short DOW|{{CURRENTDOW}}}} gives "

For 3, see Array (disambiguation)."

{{for|call=Short DOW|7}} gives "

For 7, see Array (disambiguation)."

{{for|call=Short DOW|sep=-|3|{{CURRENTDOW}}|7}} gives "

For 3, see 3 and 7."

{{for|call=Short DOW|6|3|5|3}} gives "

For 6, see 3 and 5."

Compare the array technique using parameter defaults, and (for final display only) that using CSS, both above.

Differences:

  • Above only one template is used instead of three.
  • Above the results are in standard index order, here in the order of the parameters in the template call.
  • Above multiple occurrences are removed.

See also

  • w:en:Portal:Middle-earth/Featured article called in w:en:Portal:Middle-earth - array technique based on parameter defaults
  • en:Template:Locale length (talk, backlinks, edit) - this template and some of its older versions apply several array techniques
  • Help:Array (older methods)
  • Attribute - array where each index value is an existing pagename, and the array value is defined on that page. If the array values are also pagenames (not necessarily existing) the array is called a relation. Compare:
    • {{#switch:3|1=Mon|2=Tue|3=Wed|4=Thu|5=Fri|6=Sat|7=Son|undefined}} gives Wed (see above)
    • <ask>weekday number:=3</ask> giving Wednesday [1]


edit

Wikipedia-specific help

Template:Ph:Array

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:Array. For Wikipedia-specific issues, use Template:Ph:Array (the extra text at the bottom of this page) or Template:Phh:Array for a Wikipedia-specific lead (text appears at the top of this page). You are welcome to copy the exact wikitext from the master page at Meta and paste it into this page at any time. To view this page in other languages see the master page at Meta.

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