Module:Params/doc

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The {{#invoke:params}} module is designed to be adopted by those templates that want to have a deep control of their parameters. It is particularly useful to variadic templates, to which it offers the possibility to count, list, map and propagate the parameters received without knowing their number in advance.

The module offers elegant shortcuts to non variadic templates as well. Outside templates the module has virtually no applications; hence, if you plan to make experiments, make sure to do them from within a template, or you will not be able to see much.

Among the possibilities that the module offers there is that of performing a series of actions after novel arguments have been concatenated to the template's incoming parameters. As this sometimes makes it necessary to keep the argument slots clean from interferences, instead of named arguments in order to specify options this module uses piping functions (i.e. functions that expect to be piped instead of returning to the caller), or modifiers. This creates a syntax similar to the following example:

{{#invoke:params|[modifier]|[...]|[modifier]|[...]|function|[...]}}

For instance, as the name suggests, the list function lists the parameters wherewith a template was called; if we imagined a template named {{Example template}} containing the following wikitext,

{{#invoke:params|list|</dd><dt>|</dt><dd>|<dl><dt>|</dd></dl>}}

and such template were called with the following arguments,

{{Example template|Beast of Bodmin=A large feline inhabiting Bodmin Moor.|Morgawr=A sea serpent.|Owlman=A giant owl-like creature.}}

the following result would be produced:

Beast of Bodmin
A large feline inhabiting Bodmin Moor.
Morgawr
A sea serpent.
Owlman
A giant owl-like creature.

However, by placing the with_name_matching modifier before the list function we would be able to filter some parameters out – such as, for instance, all parameter names that do not end with an “n”:

{{#invoke:params|with_name_matching|n$|list|</dd><dt>|</dt><dd>|<dl><dt>|</dd></dl>}}

Thus, the previous code would produce:

Beast of Bodmin
A large feline inhabiting Bodmin Moor.
Owlman
A giant owl-like creature.

This mechanism has the intrinsic advantage that it allows to concatenate infinite modifiers. And so, in order to get the accurate result that we want to obtain we could write:

{{#invoke:params|with_name_matching|n$|with_name_matching|^A|non-sequential|with_name_matching|banana|list}}

The two modifiers sequential and non-sequential refer to a technical jargon used in wikitext: given a parameter list, the subgroup of sequential parameters is constituted by the largest group of consecutive numerical parameters starting from |1= – this is known as the parameters' “sequence”. A parameter list that does not have a first parameter specified does not possess a sequence.

Functions

Here follows the list of functions. All modifiers are applicable to all of them (see § Modifiers).

count

Brief
Count the number of parameters whereby a template was called
Syntax
{{#invoke:params|count}}

This function does not take arguments.

value_of

Brief
Get the value of a single parameter
Syntax
{{#invoke:params|value_of|parameter name|[header]|[footer]}}

Without modifiers this function is similar to writing {{{parameter name|}}} – with optional header and footer to be displayed only when the parameter is found. With modifiers, however, it allows to reach parameters that would be unreachable without knowing their number in advance. For instance, writing

{{#invoke:params|trimmed|-2|0|value_of|1}}

will write the value of the second-last sequential parameter, independently of how many parameters the template was called with. If no matching parameter is found this function expands to nothing.

  Note: The header (|2=) and footer (|3=) arguments are not trimmed of their leading and trailing spaces. The value_of function name itself and the parameter name (|1=), on the other hand, will be trimmed of their surrounding spaces.

list

Brief
List the template parameters (both their names and their values)
Syntax
{{#invoke:params|list|[argument separator]|[key-value separator]|[header]|[footer]}}

If no arguments are passed the vertical bar (|) will be used as parameter separator and the equals sign (=) will be used as key-value separator, with no header and no footer.

  Note: All arguments passed to this function are not trimmed of their leading and trailing spaces. The list function name itself, however, can be surrounded by spaces.

list_values

Brief
List the template parameter values
Syntax
{{#invoke:params|list_values|[argument separator]|[header]|[footer]}}

If no arguments are passed the vertical bar (|) will be used as parameter separator, with no header and no footer.

  Note: All arguments passed to this function are not trimmed of their leading and trailing spaces. The list_values function name itself, however, can be surrounded by spaces.

concat_and_call

Brief
Prepend user-given unnamed arguments to the current parameters, or impose user-given named arguments; then propagate everything to a custom template
Syntax
{{#invoke:params|concat_and_call|template name|[prepend 1]|[prepend 2]|[...]|[prepend n]|[named item 1=value 1]|[...]|[named item n=value n]|[...] }}

For example, if our {{Example template}} had the following code,

{{#invoke:params|concat_and_call|foo bar|elbow|earth|room|7=classy|hello=not today}}

and it were called with,

{{example template|one|two|three|hello=world|wind=spicy}}

the following call to the {{Foo bar}} template would be performed:

{{foo bar|elbow|earth|room|7=classy|8=one|9=two|10=three|wind=spicy|hello=not today}}

If no other argument besides the template name are provided this function simply echoes the current parameters to another template.

  Note: All arguments passed to this function except the template name are not trimmed of their leading and trailing spaces. The concat_and_call function name itself, however, can be surrounded by spaces.

concat_and_invoke

Brief
Prepend user-given unnamed arguments to the current parameters, or impose user-given named arguments; then propagate everything to a custom module
Syntax
{{#invoke:params|concat_and_invoke|module name|function name|[prepend 1]|[prepend 2]|[...]|[prepend n]|[named item 1=value 1]|[...]|[named item n=value n]|[...] }}

Exactly like concat_and_call, but invokes a module instead of calling a template.

  Note: All arguments passed to this function except the module name and the function name are not trimmed of their leading and trailing spaces. The concat_and_invoke function name itself, however, can be surrounded by spaces.

call_for_each

Brief
For each parameter passed to the caller template, call a custom template with at least two parameters (key and value)
Syntax
{{#invoke:params|call_for_each|template name|[append 1]|[append 2]|[...]|[append n]|[named param 1=value 1]|[...]|[named param n=value n]|[...] }}

All other unnamed parameters following the template name will be appended to the key-value pair. Named parameters will be passed verbatim.

  Note: All arguments passed to this function except the template name are not trimmed of their leading and trailing spaces. The call_for_each function name itself, however, can be surrounded by spaces.

invoke_for_each

Brief
For each parameter passed to the caller template, invoke a custom module function with at least two arguments (key and value)
Syntax
{{#invoke:params|invoke_for_each|module name|module function|[append 1]|[append 2]|[...]|[append n]|[named param 1=value 1]|[...]|[named param n=value n]|[...]}}

Exactly like call_for_each, but invokes a module instead of calling a template.

  Note: All arguments passed to this function except the module name and the function name are not trimmed of their leading and trailing spaces. The invoke_for_each function name itself, however, can be surrounded by spaces.

call_for_each_value

Brief
For each parameter passed to the caller template, call a custom template with at least one parameter (i.e. the parameter's value)
Syntax
{{#invoke:params|call_for_each_value|template name|[append 1]|[append 2]|[...]|[append n]|[named param 1=value 1]|[...]|[named param n=value n]|[...]}}

All other unnamed parameters following the template name will be appended after the value parameter. Named parameters will be passed verbatim.

  Note: All arguments passed to this function except the template name are not trimmed of their leading and trailing spaces. The call_for_each_value function name itself, however, can be surrounded by spaces.

invoke_for_each_value

Brief
For each parameter passed to the caller template, invoke a custom module function with at least one argument (i.e. the parameter's value)
Syntax
{{#invoke:params|invoke_for_each_value|module name|module function|[append 1]|[append 2]|[...]|[append n]|[named param 1=value 1]|[...]|[named param n=value n]|[...]}}

Exactly like call_for_each_value, but invokes a module instead of calling a template.

  Note: All arguments passed to this function except the module name and the function name are not trimmed of their leading and trailing spaces. The invoke_for_each_value function name itself, however, can be surrounded by spaces.

for_each

Brief
For each parameter passed to the caller template, expand all occurrences of $# and $@ within a given text as key and value respectively
Syntax
{{#invoke:params|for_each|wikitext|[header]|[footer]}}

Example:

{{#invoke:params|for_each|Arg name: $#, Arg value: $@}}

  Note: All arguments passed to this function are not trimmed of their leading and trailing spaces. The for_each function name itself, however, can be surrounded by spaces.

Modifiers (piping functions)

The following are modifiers, i.e. functions that expect to be piped instead of returning to the caller. Each of them can be followed by either another modifier or a non-piping function.

sequential

Brief
Reduce the parameter list to the subgroup of consecutive parameters that follow |1=
Syntax
{{#invoke:params|sequential|pipe function name}}

Example:

{{#invoke:params|sequential|count}}

This function does not take arguments besides the name of the function that must follow.

non-sequential

Brief
Reduce the parameter list by subtracting the subgroup of consecutive parameters that follow |1=
Syntax
{{#invoke:params|non-sequential|pipe function name}}

Example:

{{#invoke:params|non-sequential|list|{{!}}|{{=}}|<nowiki>{{</nowiki>foobar{{!}}|<nowiki>}}</nowiki>}}

This function does not take arguments besides the name of the function that must follow.

with_name_matching

Brief
Remove from the parameter list all the parameters whose name does not match the given pattern
Syntax
{{#invoke:params|with_name_matching|pattern|pipe function name}}

Internally this modifier uses Lua's string.find() function to find whether parameter names match against a given pattern. For the pattern argument (|1=) please use the same syntax of Lua patterns.

Example:

{{#invoke:params|with_name_matching|n$|list|</dd><dt>|</dt><dd>|<dl><dt>|</dd></dl>}}

  Note: The argument passed to this function is not trimmed of its leading and trailing spaces. The with_name_matching function name itself, however, can be surrounded by spaces.

with_name_not_matching

Brief
Remove from the parameter list all the parameters whose name matches the given pattern
Syntax
{{#invoke:params|with_name_not_matching|pattern|pipe function name}}

Internally this modifier uses Lua's string.find() function to find whether parameter names match against a given pattern. For the pattern argument (|1=) please use the same syntax of Lua patterns.

Example:

{{#invoke:params|with_name_not_matching|n$|count}}

  Note: The argument passed to this function is not trimmed of its leading and trailing spaces. The with_name_not_matching function name itself, however, can be surrounded by spaces.

with_value_matching

Brief
Remove from the parameter list all the parameters whose value does not match the given pattern
Syntax
{{#invoke:params|with_value_matching|pattern|pipe function name}}

Internally this modifier uses Lua's string.find() function to find whether parameter values match against a given pattern. For the pattern argument (|1=) please use the same syntax of Lua patterns.

Example:

{{#invoke:params|with_value_matching|n$|count}}

  Note: The argument passed to this function is not trimmed of its leading and trailing spaces. The with_value_matching function name itself, however, can be surrounded by spaces.

with_value_not_matching

Brief
Remove from the parameter list all the parameters whose value matches the given pattern
Syntax
{{#invoke:params|with_value_not_matching|pattern|pipe function name}}

Internally this modifier uses Lua's string.find() function to find whether parameter values match against a given pattern. For the pattern argument (|1=) please use the same syntax of Lua patterns.

Example:

{{#invoke:params|with_value_not_matching|n$|count}}

  Note: The argument passed to this function is not trimmed of its leading and trailing spaces. The with_value_not_matching function name itself, however, can be surrounded by spaces.

trimmed

Brief
Remove zero or more parameters from the beginning and the end of the parameter list
Syntax
{{#invoke:params|trimmed|left trim|right trim|pipe function name}}

The first argument indicates how many sequential parameters must be removed from the beginning of the parameter list, the second argument indicates how many sequential parameters must be removed from the end of the parameter list. If any of the two arguments is a negative number its absolute value indicates what must be left on the other side – i.e. {{#invoke:params|trimmed|-3|0|list}} indicates that the last three arguments must be listed.

Example:

{{#invoke:params|trimmed|0|2|sequential|call_for_each_value|example template}}

  Note: Although {{#invoke:params|trimmed|-1|1|...}} de facto gets rid of all sequential parameters, it is more efficient to do {{#invoke:params|non-sequential|...}} to obtain the same effect.

In some cases it might be necessary to concatenate more than one invocation of the trimmed function. For instance, notice the |trimmed|1|0|trimmed|-1|0 code in the following imaginary {{Foobar see also}} template in order to properly show the “and” conjunction and possibly an Oxford comma when more than two page names are provided:

{{Hatnote|{{{altphrase|Foobar see also}}}: {{#if:{{{1|}}}
		|[[{{{1}}}]]{{#invoke:params|sequential|trimmed|1|1|for_each|, [[$@]]}}{{#invoke:params|sequential|trimmed|1|0|trimmed|-1|0|for_each| and [[$@]]|{{#if:{{{3|}}}|,}}}}
		|{{Error|{{tl|Foobar see also}} requires at least one page name}}
	}}
}}

See also