String::Formatter::Cookbook(3p)

NAME
String::Formatter::Cookbook - ways to put String::Formatter to use

VERSION
version 1.235

OVERVIEW
String::Formatter is a pretty simple system for building formatting routines, but it can be hard to get started without an idea of the sort of things that are possible.

PERL VERSION
This library should run on perls released even a long time ago. It should work on any version of perl released in the last five years.

Although it may work on older versions of perl, no guarantee is made that the minimum required version will not be increased. The version may be increased for any reason, and there is no promise that patches will be accepted to lower the minimum required perl.

BASIC RECIPES

  constants only
The simplest stringf interface you can provide is one that just formats constant strings, allowing the user to put them inside other fixed strings with alignment:

  use String::Formatter stringf => {
    input_processor => 'forbid_input',
    codes => {
      a => 'apples',
      b => 'bananas',
      w => 'watermelon',
    },
  };

  print stringf('I eat %a and %b but never %w.');

  # Output:
  # I eat apples and bananas but never watermelon.

If the user tries to parameterize the string by passing arguments after the format string, an exception will be raised.

  sprintf-like conversions
Another common pattern is to create a routine that behaves like Perl's "sprintf", but with a different set of conversion routines. (It will also almost certainly have much simpler semantics than Perl's wildly complex behavior.)

  use String::Formatter stringf => {
    codes => {
      s => sub { $_ },     # string itself
      l => sub { length }, # length of input string
      e => sub { /[^\x00-\x7F]/ ? '8bit' : '7bit' }, # ascii-safeness
    },
  };

  print stringf(
    "My name is %s.  I am about %l feet tall.  I use an %e alphabet.\n",
    'Ricardo',
    'ffffff',
    'abcchdefghijklllmnñopqrrrstuvwxyz',
  );

  # Output:
  # My name is Ricardo.  I am about 6 feet tall.  I use an 8bit alphabet.

Warning: The behavior of positional string replacement when the conversion codes mix constant strings and code references is currently poorly nailed-down. Do not rely on it yet.

  named conversions
This recipe acts a bit like Python's format operator when given a dictionary. Rather than matching format code position with input ordering, inputs can be chosen by name.

  use String::Formatter stringf => {
    input_processor => 'require_named_input',
    string_replacer => 'named_replace',

    codes => {
      s => sub { $_ },     # string itself
      l => sub { length }, # length of input string
      e => sub { /[^\x00-\x7F]/ ? '8bit' : '7bit' }, # ascii-safeness
    },
  };

  print stringf(
    "My %{which}s name is %{name}s.  My name is %{name}l letters long.",
    {
      which => 'first',
      name  => 'Marvin',
    },
  );

  # Output:
  # My first name is Marvin.  My name is 6 letters long.

Because this is a useful recipe, there is a shorthand for it:

  use String::Formatter named_stringf => {
    codes => {
      s => sub { $_ },     # string itself
      l => sub { length }, # length of input string
      e => sub { /[^\x00-\x7F]/ ? '8bit' : '7bit' }, # ascii-safeness
    },
  };

  method calls
Some objects provide methods to stringify them flexibly. For example, many objects that represent timestamps allow you to call "strftime" or something similar. The "method_replace" string replacer comes in handy here:

  use String::Formatter stringf => {
    input_processor => 'require_single_input',
    string_replacer => 'method_replace',

    codes => {
      f => 'strftime',
      c => 'format_cldr',
      s => sub { "$_[0]" },
    },
  };

  print stringf(
    "%{%Y-%m-%d}f is also %{yyyy-MM-dd}c.  Default string is %s.",
    DateTime->now,
  );

  # Output:
  # 2009-11-17 is also 2009-11-17.  Default string is 2009-11-17T15:35:11.

This recipe is available as the export "method_stringf":

  use String::Formatter method_stringf => {
    codes => {
      f => 'strftime',
      c => 'format_cldr',
      s => sub { "$_[0]" },
    },
  };

You can easily use this to implement an actual stringf-like method:

  package MyClass;

  use String::Formatter method_stringf => {
    -as => '_stringf',
    codes => {
      f => 'strftime',
      c => 'format_cldr',
      s => sub { "$_[0]" },
    },
  };

  sub format {
    my ($self, $format) = @_;
    return _stringf($format, $self);
  }

AUTHORS

•   Ricardo Signes <cpan@semiotic.systems>

•   Darren Chamberlain <darren@cpan.org>

COPYRIGHT AND LICENSE
This software is Copyright (c) 2022 by Ricardo Signes <cpan@semiotic.systems>.

This is free software, licensed under:

  The GNU General Public License, Version 2, June 1991