phpMan > man > Params::Check

NAME
    Params::Check - A generic input parsing/checking mechanism.

SYNOPSIS
        use Params::Check qw[check allow last_error];

        sub fill_personal_info {
            my %hash = @_;
            my $x;

            my $tmpl = {
                firstname   => { required   => 1, defined => 1 },
                lastname    => { required   => 1, store => \$x },
                gender      => { required   => 1,
                                 allow      => [qr/M/i, qr/F/i],
                               },
                married     => { allow      => [0,1] },
                age         => { default    => 21,
                                 allow      => qr/^\d+$/,
                               },

                phone       => { allow => [ sub { return 1 if /$valid_re/ },
                                            '1-800-PERL' ]
                               },
                id_list     => { default        => [],
                                 strict_type    => 1
                               },
                employer    => { default => 'NSA', no_override => 1 },
            };

            ### check() returns a hashref of parsed args on success ###
            my $parsed_args = check( $tmpl, \%hash, $VERBOSE )
                                or die qw[Could not parse arguments!];

            ... other code here ...
        }

        my $ok = allow( $colour, [qw|blue green yellow|] );

        my $error = Params::Check::last_error();

DESCRIPTION
    Params::Check is a generic input parsing/checking mechanism.

    It allows you to validate input via a template. The only requirement is that the arguments must
    be named.

    Params::Check can do the following things for you:

    *   Convert all keys to lowercase

    *   Check if all required arguments have been provided

    *   Set arguments that have not been provided to the default

    *   Weed out arguments that are not supported and warn about them to the user

    *   Validate the arguments given by the user based on strings, regexes, lists or even
        subroutines

    *   Enforce type integrity if required

    Most of Params::Check's power comes from its template, which we'll discuss below:

Template
    As you can see in the synopsis, based on your template, the arguments provided will be
    validated.

    The template can take a different set of rules per key that is used.

    The following rules are available:

    default
        This is the default value if none was provided by the user. This is also the type
        "strict_type" will look at when checking type integrity (see below).

    required
        A boolean flag that indicates if this argument was a required argument. If marked as
        required and not provided, check() will fail.

    strict_type
        This does a "ref()" check on the argument provided. The "ref" of the argument must be the
        same as the "ref" of the default value for this check to pass.

        This is very useful if you insist on taking an array reference as argument for example.

    defined
        If this template key is true, enforces that if this key is provided by user input, its value
        is "defined". This just means that the user is not allowed to pass "undef" as a value for
        this key and is equivalent to: allow => sub { defined $_[0] && OTHER TESTS }

    no_override
        This allows you to specify "constants" in your template. ie, they keys that are not allowed
        to be altered by the user. It pretty much allows you to keep all your "configurable" data in
        one place; the "Params::Check" template.

    store
        This allows you to pass a reference to a scalar, in which the data will be stored:

            my $x;
            my $args = check(foo => { default => 1, store => \$x }, $input);

        This is basically shorthand for saying:

            my $args = check( { foo => { default => 1 }, $input );
            my $x    = $args->{foo};

        You can alter the global variable $Params::Check::NO_DUPLICATES to control whether the
        "store"'d key will still be present in your result set. See the "Global Variables" section
        below.

    allow
        A set of criteria used to validate a particular piece of data if it has to adhere to
        particular rules.

        See the "allow()" function for details.

Functions
  check( \%tmpl, \%args, [$verbose] );
    This function is not exported by default, so you'll have to ask for it via:

        use Params::Check qw[check];

    or use its fully qualified name instead.

    "check" takes a list of arguments, as follows:

    Template
        This is a hash reference which contains a template as explained in the "SYNOPSIS" and
        "Template" section.

    Arguments
        This is a reference to a hash of named arguments which need checking.

    Verbose
        A boolean to indicate whether "check" should be verbose and warn about what went wrong in a
        check or not.

        You can enable this program wide by setting the package variable $Params::Check::VERBOSE to
        a true value. For details, see the section on "Global Variables" below.

    "check" will return when it fails, or a hashref with lowercase keys of parsed arguments when it
    succeeds.

    So a typical call to check would look like this:

        my $parsed = check( \%template, \%arguments, $VERBOSE )
                        or warn q[Arguments could not be parsed!];

    A lot of the behaviour of "check()" can be altered by setting package variables. See the section
    on "Global Variables" for details on this.

  allow( $test_me, \@criteria );
    The function that handles the "allow" key in the template is also available for independent use.

    The function takes as first argument a key to test against, and as second argument any form of
    criteria that are also allowed by the "allow" key in the template.

    You can use the following types of values for allow:

    string
        The provided argument MUST be equal to the string for the validation to pass.

    regexp
        The provided argument MUST match the regular expression for the validation to pass.

    subroutine
        The provided subroutine MUST return true in order for the validation to pass and the
        argument accepted.

        (This is particularly useful for more complicated data).

    array ref
        The provided argument MUST equal one of the elements of the array ref for the validation to
        pass. An array ref can hold all the above values.

    It returns true if the key matched the criteria, or false otherwise.

  last_error()
    Returns a string containing all warnings and errors reported during the last time "check" was
    called.

    This is useful if you want to report then some other way than "carp"'ing when the verbose flag
    is on.

    It is exported upon request.

Global Variables
    The behaviour of Params::Check can be altered by changing the following global variables:

  $Params::Check::VERBOSE
    This controls whether Params::Check will issue warnings and explanations as to why certain
    things may have failed. If you set it to 0, Params::Check will not output any warnings.

    The default is 1 when warnings are enabled, 0 otherwise;

  $Params::Check::STRICT_TYPE
    This works like the "strict_type" option you can pass to "check", which will turn on
    "strict_type" globally for all calls to "check".

    The default is 0;

  $Params::Check::ALLOW_UNKNOWN
    If you set this flag, unknown options will still be present in the return value, rather than
    filtered out. This is useful if your subroutine is only interested in a few arguments, and wants
    to pass the rest on blindly to perhaps another subroutine.

    The default is 0;

  $Params::Check::STRIP_LEADING_DASHES
    If you set this flag, all keys passed in the following manner:

        function( -key => 'val' );

    will have their leading dashes stripped.

  $Params::Check::NO_DUPLICATES
    If set to true, all keys in the template that are marked as to be stored in a scalar, will also
    be removed from the result set.

    Default is false, meaning that when you use "store" as a template key, "check" will put it both
    in the scalar you supplied, as well as in the hashref it returns.

  $Params::Check::PRESERVE_CASE
    If set to true, Params::Check will no longer convert all keys from the user input to lowercase,
    but instead expect them to be in the case the template provided. This is useful when you want to
    use similar keys with different casing in your templates.

    Understand that this removes the case-insensitivity feature of this module.

    Default is 0;

  $Params::Check::ONLY_ALLOW_DEFINED
    If set to true, Params::Check will require all values passed to be "defined". If you wish to
    enable this on a 'per key' basis, use the template option "defined" instead.

    Default is 0;

  $Params::Check::SANITY_CHECK_TEMPLATE
    If set to true, Params::Check will sanity check templates, validating for errors and unknown
    keys. Although very useful for debugging, this can be somewhat slow in hot-code and large loops.

    To disable this check, set this variable to "false".

    Default is 1;

  $Params::Check::WARNINGS_FATAL
    If set to true, Params::Check will "croak" when an error during template validation occurs,
    rather than return "false".

    Default is 0;

  $Params::Check::CALLER_DEPTH
    This global modifies the argument given to "caller()" by "Params::Check::check()" and is useful
    if you have a custom wrapper function around "Params::Check::check()". The value must be an
    integer, indicating the number of wrapper functions inserted between the real function call and
    "Params::Check::check()".

    Example wrapper function, using a custom stacktrace:

        sub check {
            my ($template, $args_in) = @_;

            local $Params::Check::WARNINGS_FATAL = 1;
            local $Params::Check::CALLER_DEPTH = $Params::Check::CALLER_DEPTH + 1;
            my $args_out = Params::Check::check($template, $args_in);

            my_stacktrace(Params::Check::last_error) unless $args_out;

            return $args_out;
        }

    Default is 0;

Acknowledgements
    Thanks to Richard Soderberg for his performance improvements.

BUG REPORTS
    Please report bugs or other issues to <bug-params-check AT rt.org>.

AUTHOR
    This module by Jos Boumans <kane AT cpan.org>.

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