String::Interpolate::Named(3p)

NAME
String::Interpolate::Named - Interpolated named arguments in string

SYNOPSIS
    use String::Interpolate::Named;

    my $ctl = { args => { fn => "Johan", ln => "Bach" } };
    say interpolate( $ctl, "The famous %{fn} %{ln}." );

    # If you like object orientation.
    my $int = String::Interpolate::Named->new( { args => { ... } } );
    say $int->interpolate("The famous %{fn} %{ln}.");

DESCRIPTION
String::Interpolate::Named provides a function to interpolate named arguments by target texts in a template string. The target texts are provided to the function via a hash, where the keys correspond to the named argument to be replaced.

  Named Arguments
The arguments to be replaced are marked in the template by enclosing them between "%{" and "}". For example, the string "The famous %{fn} %{ln}." contains two named arguments, "fn" and "ln".

  Basic Interpolation
When interpolated, the keys "fn" and "ln" are looked up in the hash, and the corresponding values are substituted. If no value was found for a named argument, nothing is substituted and the "%{...}" is removed.

You can precede "%", "{", "}" (and "|", see below) with a backslash "\" to hide their special meanings. For example, "\}" will not be considered closing an argument but yield a plain "}" in the text.

  Conditional Interpolation
It is possible to select replacement values depending on whether the named argument has a value or not:

    "This book has %{title|title %{title}}"
    "This book has %{title|title %{title}|no title}"

These are considered "%{if|then}" and "%{if|then|else}" cases.

Assuming argument "title" has the value "My Book", in the first example the text "title My Book", the 'then' text, will be substituted, resulting in

    "This book has title My Title"

If "title" does not have a value, the empty string is substituted. In the second example, the string "no title", the 'else' text, will be substituted.

As can be seen, the replacement texts may contain interpolations as well. For convenience, you can use "%{}" to refer to the value of the named argument currently being examinated. The last example above can be written more shortly and elegantly as:

    "This book has %{title|title %{}|no title}"

  Testing Values
Instead of testing for named variables to have a value, you can also test for specific values:

    "This takes %{days=1|%{} day|%{} days}"

  List Values
The replacement values hash may be scalar (in general: strings and numbers) or lists of scalars. If a value is a list of scalars, it is possible to select a particular value from the list by appending an index (period and a number) to the named argument.

Assume "customer" has value "[ "Jones", "Smith" ]", then:

    "%{customer.1} will be Smith"
    "%{customer.2} will be Jones"
    "%{customer} will be Jones Smith"

When no element is selected the values are concatenated.

  The Control Hash
The interpolation process requires two parameters: a hash with settings and values for the named arguments, and the string to be used as a template for interpolation. The hash will be further referred to as the control hash.

The hash can have the following keys:

vars
    This is the hash that contains replacement texts for the named variables.

    This element should be considered mandatory.

separator
    The separator used to concatenate list values, see "List Values" above.

    It defaults to Perl variable $" that, on its turn, defaults to a single space.

maxiter
    To enable nested substitutions and recursive replacement, the interpolation process is repeated until there are no more interpolations to be made. The maximun number of iterations is limited to the value of "maxiter".

    By default maxiter is 16.

An example of a control hash:

    my %ctl =
      ( args => {
          customer => [ "Jones", "Smith" ],
          days     => 2,
          title    => "My Title",
        },
        separator => ", ",
      );

  Object Oriented API
    my $ii = String::Interpolate::Named->new;
    $ii->ctl(\%ctl);
    $result = $ii->interpolate($template);

For convenience, the control hash may be passed to the constructor:

    my $ii = String::Interpolate::Named->new(\%ctl);
    $result = $ii->interpolate($template);

  Functional API
String::Interpolate::Named privides a single function, "interpolate", which is exported by default.

The subroutine takes two arguments: a reference to a control hash and the template string.

   $result = interpolate( \%ctl, $template );

METHODS

  new
Constructs a new String::Interpolate::Named object.

    my $ii = String::Interpolate::Named->new;

or

    my $ii = String::Interpolate::Named->new(\%ctl);

  ctl
Associates a control has with an existing object.

    $ii->ctl(\%ctl);

  interpolate
This routine performs the actual interpolations. It can be used as a method:

    $ii->interpolate($template);

and functional:

    interpolate( \%ctl, $template );

REQUIREMENTS
Minimal Perl version 5.10.1.

AUTHOR
Johan Vromans, "<JV at CPAN dot org>"

SUPPORT
Development of this module takes place on GitHub: <https://github.com/sciurius/perl-String-Interpolate-Named>.

You can find documentation for this module with the perldoc command.

    perldoc String::Interpolate::Named

Please report any bugs or feature requests using the issue tracker on GitHub.

ACKNOWLEDGEMENTS
Many of the existing template / interpolate / substitute modules.

COPYRIGHT & LICENSE
Copyright 2018,2019 Johan Vromans, all rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.