X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=lib%2FUNIVERSAL.pm;h=8808271ef9837032d1c129544ec3b0eaf5e1f1b2;hb=8af3c3489f0c9ca8d37ebae27991ac4f34dfdb2f;hp=c0e7ebdee2b2a0f5b2d9e43cc5a64c34ac454774;hpb=7e1af8bca57f405a8444b575a870918a6d88fc5c;p=p5sagit%2Fp5-mst-13.2.git diff --git a/lib/UNIVERSAL.pm b/lib/UNIVERSAL.pm index c0e7ebd..8808271 100644 --- a/lib/UNIVERSAL.pm +++ b/lib/UNIVERSAL.pm @@ -1,8 +1,22 @@ package UNIVERSAL; +our $VERSION = '1.02'; + +# UNIVERSAL should not contain any extra subs/methods beyond those +# that it exists to define. The use of Exporter below is a historical +# accident that can't be fixed without breaking code. Note that we +# *don't* set @ISA here, don't want all classes/objects inheriting from +# Exporter. It's bad enough that all classes have a import() method +# whenever UNIVERSAL.pm is loaded. require Exporter; -@ISA = qw(Exporter); -@EXPORT_OK = qw(isa); +@EXPORT_OK = qw(isa can VERSION); + +# Make sure that even though the import method is called, it doesn't do +# anything unless its called on UNIVERSAL +sub import { + return unless $_[0] eq __PACKAGE__; + goto &Exporter::import; +} 1; __END__ @@ -13,69 +27,127 @@ UNIVERSAL - base class for ALL classes (blessed references) =head1 SYNOPSIS - use UNIVERSAL qw(isa); + $is_io = $fd->isa("IO::Handle"); + $is_io = Class->isa("IO::Handle"); + + $sub = $obj->can("print"); + $sub = Class->can("print"); - $yes = isa($ref, "HASH"); - $io = $fd->isa("IO::Handle"); - $sub = $obj->can('print'); + use UNIVERSAL qw( isa can VERSION ); + $yes = isa $ref, "HASH" ; + $sub = can $ref, "fandango" ; + $ver = VERSION $obj ; =head1 DESCRIPTION C is the base class which all bless references will inherit from, -see L +see L. -C provides the following methods +C provides the following methods and functions: =over 4 -=item isa ( TYPE ) +=item C<< $obj->isa( TYPE ) >> -C returns I if C is blessed into package C -or inherits from package C. +=item C<< CLASS->isa( TYPE ) >> -C can be called as either a static or object method call. +=item C -=item can ( METHOD ) +Where -C checks if the object has a method called C. If it does -then a reference to the sub is returned. If it does not then I -is returned. +=over 4 -C can be called as either a static or object method call. +=item C -=item VERSION ( [ REQUIRE ] ) +is a package name -C will return the value of the variable C<$VERSION> in the -package the object is blessed into. If C is given then -it will do a comparison and die if the package version is not -greater than or equal to C. +=item C<$obj> -C can be called as either a static or object method call. +is a blessed reference or a string containing a package name + +=item C + +is a package name + +=item C + +is any of the above or an unblessed reference =back -C also optionally exports the following subroutines +When used as an instance or class method (C<< $obj->isa( TYPE ) >>), +C returns I if $obj is blessed into package C or +inherits from package C. -=over 4 +When used as a class method (C<< CLASS->isa( TYPE ) >>: sometimes +referred to as a static method), C returns I if C +inherits from (or is itself) the name of the package C or +inherits from package C. -=item isa ( REF, TYPE ) +When used as a function, like -C returns I if the first argument is a reference and either -of the following statements is true. + use UNIVERSAL qw( isa ) ; + $yes = isa $h, "HASH"; + $yes = isa "Foo", "Bar"; -=over 8 +or -=item + require UNIVERSAL ; + $yes = UNIVERSAL::isa $a, "ARRAY"; -C is a blessed reference and is blessed into package C -or inherits from package C +C returns I in the same cases as above and also if C is an +unblessed reference to a perl variable of type C, such as "HASH", +"ARRAY", or "Regexp". -=item +=item C<< $obj->can( METHOD ) >> -C is a reference to a C of perl variable (er 'HASH') +=item C<< CLASS->can( METHOD ) >> + +=item C + +C checks if the object or class has a method called C. If it does +then a reference to the sub is returned. If it does not then I is +returned. This includes methods inherited or imported by C<$obj>, C, or +C. + +C cannot know whether an object will be able to provide a method +through AUTOLOAD, so a return value of I does not necessarily mean +the object will not be able to handle the method call. To get around +this some module authors use a forward declaration (see L) +for methods they will handle via AUTOLOAD. For such 'dummy' subs, C +will still return a code reference, which, when called, will fall through +to the AUTOLOAD. If no suitable AUTOLOAD is provided, calling the coderef +will cause an error. + +C can be called as a class (static) method, an object method, or a +function. + +When used as a function, if C is a blessed reference or package name which +has a method called C, C returns a reference to the subroutine. +If C is not a blessed reference, or if it does not have a method +C, I is returned. + +=item C + +C will return the value of the variable C<$VERSION> in the +package the object is blessed into. If C is given then +it will do a comparison and die if the package version is not +greater than or equal to C. + +C can be called as either a class (static) method, an object +method or a function. -=back =back +=head1 EXPORTS + +None by default. + +You may request the import of all three functions (C, C, and +C), however it isn't usually necessary to do so. Perl magically +makes these functions act as methods on all objects. The one exception is +C, which is useful as a function when operating on non-blessed +references. + =cut