DateTime::Format::Builder::Parser - Parser creation
version 0.83
my $class = 'DateTime::Format::Builder::Parser';
my $parser = $class->create_single_parser(%specs);
This is a utility class for the DateTime::Format::Builder manpage that handles creation
of parsers. It is to here that Builder delegates most of its
responsibilities.
There are two sorts of methods in this class. Those used by parser
implementations and those used by Builder. It is generally unlikely the
user will want to use any of them.
They are presented, grouped according to use.
These methods allow implementations to have validation of their arguments in a
standard manner and due to Parser's implementation, these methods also
allow Parser to determine which implementation to use.
These parameters appear for all parser implementations. These are primarily
documented in the DateTime::Format::Builder manpage.
- on_match
- on_fail
- postprocess
- preprocess
- label
- length
length may be a number or an arrayref of numbers indicating the length of
the input. This lets us optimize in the case of static length input. If
supplying an arrayref of numbers, please keep the number of numbers to a
minimum.
my $params = $self->params;
validate( @_, $params );
Returns declared parameters and common parameters in a hashref suitable for
handing to the Params::Validate manpage's validate function.
my $all_params = $self->params_all;
Returns a hash of all the valid options. Not recommended for general use.
__PACKAGE__->valid_params(%params);
Arguments are as per the Params::Validate manpage's validate function. This method
is used to declare what your valid arguments are in a parser specification.
my $class = whose_params( $key );
Internal function which merely returns to which class a parameter is
unique. If not unique, returns undef.
This takes a single specification and returns a coderef that is a parser that
suits that specification. This is the end of the line for all the parser
creation methods. It delegates no further.
If a coderef is specified, then that coderef is immediately returned (it is
assumed to be appropriate).
The single specification (if not a coderef) can be either a hashref or a
hash. The keys and values must be as per the specification.
It is here that any arrays of callbacks are unified. It is also here that any
parser implementations are used. With the spec that's given, the keys are
looked at and whichever module is the first to have a unique key in the spec
is the one to whom the spec is given.
Note: please declare a valid_params argument with an uppercase
letter. For example, if you're writing
DateTime::Format::Builder::Parser::Fnord, declare a parameter called
Fnord. Similarly, DTFBP::Strptime should have Strptime and
DTFBP::Regex should have Regex. These latter two don't for backwards
compatibility reasons.
The returned parser will return either a DateTime object or undef.
Produce either undef or a single coderef from either undef, an empty array, a
single coderef or an array of coderefs
Given the options block (as made from create_parser) and a list of single
parser specifications, this returns a coderef that returns either the
resultant DateTime object or undef.
It first sorts the specifications using sort_parsers and then creates the
function based on what that returned.
This takes the list of specifications and sorts them while turning the
specifications into parsers. It returns two values: the first is a hashref
containing all the length based parsers. The second is an array containing all
the other parsers.
If any of the specs are not code or hash references, then it will call
croak.
Code references are put directly into the 'other' array. Any hash references
without length keys are run through create_single_parser and the
resultant parser is placed in the 'other' array.
Hash references with length keys are run through
create_single_parser, but the resultant parser is used as the value in the
length hashref with the length being the key. If two or more parsers have the
same length specified then an error is thrown.
create_class is mostly a wrapper around create_parser that does loops
and stuff and calls create_parser to create the actual parsers.
create_parser takes the parser specifications (be they single
specifications or multiple specifications) and returns an anonymous coderef
that is suitable for use as a method. The coderef will call croak in the
event of being unable to parse the single string it expects as input.
The simplest input is that of a single specification, presented just as a
plain hash, not a hashref. This is passed directly to create_single_parser
with the return value from that being wrapped in a function that lets it
croak on failure, with that wrapper being returned.
If the first argument to create_parser is an arrayref, then that is taken
to be an options block (as per the multiple parser specification documented
earlier).
Any further arguments should be either hashrefs or coderefs. If the first
argument after the optional arrayref is not a hashref or coderef then that
argument and all remaining arguments are passed off to create_single_parser
directly. If the first argument is a hashref or coderef, then it and the
remaining arguments are passed to create_multiple_parsers.
The resultant coderef from calling either of the creation methods is then
wrapped in a function that calls croak in event of failure or the
DateTime object in event of success.
Parser automatically loads any parser classes in @INC.
To be loaded automatically, you must be a
DateTime::Format::Builder::Parser::XXX module.
To be invisible, and not loaded, start your class with a lower class
letter. These are ignored.
Create a module and name it in the form
DateTime::Format::Builder::Parser::XXX where XXX is whatever you like,
so long as it doesn't start with a lower case letter.
Alternatively, call it something completely different if you don't mind the
users explicitly loading your module.
I'd recommend keeping within the DateTime::Format::Builder namespace though
--- at the time of writing I've not given thought to what non-auto loaded ones
should be called. Any ideas, please email me.
Call <DateTime::Format::Builder::Parser-valid_params>> with
Params::Validate style arguments. For example:
DateTime::Format::Builder::Parser->valid_params(
params => { type => ARRAYREF },
Regex => {
type => SCALARREF,
callbacks => {
'is a regex' => sub { ref(shift) eq 'Regexp' }
}
}
);
Start one of the key names with a capital letter. Ideally that key should
match the XXX from earlier. This will be used to help identify which module
a parser specification should be given to.
The key names on_match, on_fail, postprocess, preprocess, label
and length are predefined. You are recommended to make use of them. You may
ignore length as sort_parsers takes care of that.
A class method of the name create_parser that does the following:
Its arguments are as for a normal method (i.e. class as first argument). The
other arguments are the result from a call to Params::Validate according to
your specification (the valid_params earlier), i.e. a hash of argument name
and value.
The return value should be a coderef that takes a date string as its first
argument and returns either a DateTime object or undef.
It is preferred that you support some callbacks to your parsers. In
particular, preprocess, on_match, on_fail and postprocess. See the
main Builder docs for the appropriate placing of
calls to the callbacks.
datetime@perl.org mailing list.
http://datetime.perl.org/
perl, DateTime, the DateTime::Format::Builder manpage.
the Params::Validate manpage.
the DateTime::Format::Builder::Parser::generic manpage,
the DateTime::Format::Builder::Parser::Dispatch manpage,
the DateTime::Format::Builder::Parser::Quick manpage,
the DateTime::Format::Builder::Parser::Regex manpage,
the DateTime::Format::Builder::Parser::Strptime manpage.
Bugs may be submitted at https://github.com/houseabsolute/DateTime-Format-Builder/issues.
I am also usually active on IRC as 'autarch' on irc://irc.perl.org.
The source code repository for DateTime-Format-Builder can be found at https://github.com/houseabsolute/DateTime-Format-Builder.
This software is Copyright (c) 2020 by Dave Rolsky.
This is free software, licensed under:
The Artistic License 2.0 (GPL Compatible)
The full text of the license can be found in the
LICENSE file included with this distribution.
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