diff options
Diffstat (limited to 'lib/UNIVERSAL.pm')
| -rw-r--r-- | lib/UNIVERSAL.pm | 108 |
1 files changed, 57 insertions, 51 deletions
diff --git a/lib/UNIVERSAL.pm b/lib/UNIVERSAL.pm index a9cb478b43..92b4fcd352 100644 --- a/lib/UNIVERSAL.pm +++ b/lib/UNIVERSAL.pm @@ -4,10 +4,13 @@ our $VERSION = '1.00'; # 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 should be fixed sometime. +# 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; *import = \&Exporter::import; -@EXPORT_OK = qw(isa can); +@EXPORT_OK = qw(isa can VERSION); 1; __END__ @@ -18,32 +21,62 @@ UNIVERSAL - base class for ALL classes (blessed references) =head1 SYNOPSIS - $io = $fd->isa("IO::Handle"); - $sub = $obj->can('print'); + $is_io = $fd->isa("IO::Handle"); + $is_io = Class->isa("IO::Handle"); - $yes = UNIVERSAL::isa($ref, "HASH"); + $sub = $obj->can("print"); + $sub = Class->can("print"); + + use UNIVERSAL qw( isa can VERSION ); + $yes = isa $ref, "HASH" ; + $sub = can $ref, "fandango" ; + $ver = VERSION $obj ; =head1 DESCRIPTION C<UNIVERSAL> is the base class which all bless references will inherit from, -see L<perlobj> +see L<perlobj>. -C<UNIVERSAL> provides the following methods +C<UNIVERSAL> provides the following methods and functions: =over 4 -=item isa ( TYPE ) +=item $obj->isa( TYPE ), CLASS->isa( TYPE ), isa( VAL, TYPE ) + + C<TYPE> is a package name + $obj is a blessed reference or a string containing a package name + C<CLASS> is a package name + C<VAL> is any of the above or an unblessed reference + +When used as an instance or class method (C<$obj->isa( TYPE )>), C<isa> +returns I<true> if $obj is blessed into package C<TYPE> or inherits from +package C<TYPE>. + +When used as a class method (C<CLASS->isa( TYPE )>; sometimes referred to as a +static method), C<isa> returns I<true> if C<CLASS> inherits from (or is itself) +the name of the package C<TYPE> or inherits from package C<TYPE>. + +When used as a function, like + + use UNIVERSAL qw( isa ) ; + $yes = isa $h, "HASH"; + $yes = isa "Foo", "Bar"; -C<isa> returns I<true> if C<REF> is blessed into package C<TYPE> -or inherits from package C<TYPE>. +or -C<isa> can be called as either a static or object method call. + require UNIVERSAL ; + $yes = UNIVERSAL::isa $a, "ARRAY"; -=item can ( METHOD ) +, C<isa> returns I<true> in the same cases as above and also if C<VAL> is an +unblessed reference to a perl variable of type C<TYPE>, such as "HASH", +"ARRAY", or "Regexp". -C<can> checks if the object has a method called C<METHOD>. If it does -then a reference to the sub is returned. If it does not then I<undef> -is returned. +=item $obj->can( METHOD ), CLASS->can( METHOD ), can( VAL, METHOD ) + +C<can> checks if the object or class has a method called C<METHOD>. If it does +then a reference to the sub is returned. If it does not then I<undef> is +returned. This includes methods inherited or imported by C<$obj>, C<CLASS>, or +C<VAL>. C<can> cannot know whether an object will be able to provide a method through AUTOLOAD, so a return value of I<undef> does not necessarily mean @@ -54,7 +87,13 @@ 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> can be called as either a static or object method call. +C<can> can be called as a class (static) method, an object method, or a +function. + +When used as a function, if C<VAL> is a blessed reference or package name which +has a method called C<METHOD>, C<can> returns a reference to the subroutine. +If C<VAL> is not a blessed reference, or if it does not have a method +C<METHOD>, I<undef> is returned. =item VERSION ( [ REQUIRE ] ) @@ -63,42 +102,9 @@ package the object is blessed into. If C<REQUIRE> is given then it will do a comparison and die if the package version is not greater than or equal to C<REQUIRE>. -C<VERSION> can be called as either a static or object method call. - -=back - -The C<isa> and C<can> methods can also be called as subroutines - -=over 4 - -=item UNIVERSAL::isa ( VAL, TYPE ) - -C<isa> returns I<true> if one of the following statements is true. - -=over 8 - -=item * - -C<VAL> is a reference blessed into either package C<TYPE> or a package -which inherits from package C<TYPE>. - -=item * - -C<VAL> is a reference to a C<TYPE> of Perl variable (e.g. 'HASH'). - -=item * - -C<VAL> is the name of a package that inherits from (or is itself) -package C<TYPE>. - -=back - -=item UNIVERSAL::can ( VAL, METHOD ) +C<VERSION> can be called as either a class (static) method, an object method or +or a function. -If C<VAL> is a blessed reference which has a method called C<METHOD>, -C<can> returns a reference to the subroutine. If C<VAL> is not -a blessed reference, or if it does not have a method C<METHOD>, -I<undef> is returned. =back |