NAME¶
Parse::Method::Signatures - Perl6 like method signature parser
DESCRIPTION¶
Inspired by Perl6::Signature but streamlined to just support the subset deemed
useful for TryCatch and MooseX::Method::Signatures.
TODO¶
- •
- Document the parameter return types.
- •
- Probably lots of other things
METHODS¶
There are only two public methods to this module, both of which should be called
as class methods. Both methods accept either a single (non-ref) scalar as the
value for the "input" attribute, or normal new style arguments (hash
or hash-ref).
signature¶
my $sig = Parse::Method::Signatures->signature( '(Str $foo)' )
Attempts to parse the (bracketed) method signature. Returns a value or croaks on
error.
param¶
my $param = Parse::Method::Signatures->param( 'Str $foo where { length($_) < 10 }')
Attempts to parse the specification for a single parameter. Returns value or
croaks on error.
ATTRIBUTES¶
All the attributes on this class are read-only.
Type: Str
The string to parse.
offset¶
Type: Int
Offset into "input" at which to start parsing. Useful for using with
Devel::Declare linestring
signature_class¶
Default: Parse::Method::Signatures::Sig
Type: Str (loaded on demand class name)
param_class¶
Default: Parse::Method::Signatures::Param
Type: Str (loaded on demand class name)
type_constraint_class¶
Default: Parse::Method::Signatures::TypeConstraint
Type: Str (loaded on demand class name)
Class that is used to turn the parsed type constraint into an actual
Moose::Meta::TypeConstraint object.
from_namespace¶
Type: ClassName
Let this module know which package it is parsing signatures form. This is
entirely optional, and the only effect is has is on parsing type constraints.
If this attribute is set it is passed to "type_constraint_class" which
can use it to introspect the package (commmonly for MooseX::Types exported
types). See "find_registered_constraint" in
Parse::Method::Signature::TypeConstraints for more details.
type_constraint_callback¶
Type: CodeRef
Passed to the constructor of "type_constraint_class". Default
implementation of this callback asks Moose for a type constrain matching the
name passed in. If you have more complex requirements, such as parsing types
created by MooseX::Types then you will want a callback similar to this:
# my $target_package defined elsewhere.
my $tc_cb = sub {
my ($pms_tc, $name) = @_;
my $code = $target_package->can($name);
$code ? eval { $code->() }
: $pms_tc->find_registered_constraint($name);
}
Note that the above example is better provided by providing the
"from_namespace" attribute.
CAVEATS¶
Like Perl6::Signature, the parsing of certain constructs is currently only a
'best effort' - specifically default values and where code blocks might not
successfully for certain complex cases. Patches/Failing tests welcome.
Additionally, default value specifications are not evaluated which means that no
such lexical or similar errors will not be produced by this module. Constant
folding will also not be performed.
There are certain constructs that are simply too much hassle to avoid when the
work around is simple. Currently the only cases that are known to parse wrong
are when using anonymous variables (i.e. just sigils) in unpacked arrays. Take
the following example:
method foo (ArrayRef [$, $], $some_value_we_care_about) {
In this case the $] is treated as one of perl's magic variables (specifically,
the patch level of the Perl interpreter) rather than a "$" followed
by a "]" as was almost certainly intended. The work around for this
is simple: introduce a space between the charcters:
method foo (ArrayRef [ $, $ ], $some_value_we_care_about) {
The same applies
AUTHOR¶
Ash Berlin <ash@cpan.org>.
Thanks to Florian Ragwitz <rafl@debian.org>.
Many thanks to Piers Cawley to showing me the way to refactor my spaghetti code
into something more manageable.
SEE ALSO¶
Devel::Declare which is used by most modules that use this (currently by all
modules known to the author.)
<
http://github.com/ashb/trycatch/tree>.
LICENSE¶
Licensed under the same terms as Perl itself.
This distribution copyright 2008-2009, Ash Berlin <ash@cpan.org>