GNU/Linux |
CentOS 2.1AS(Slurm) |
|
UNIVERSAL(3pm) |
UNIVERSAL − base class for ALL classes (blessed references)
$io = $fd->isa("IO::Handle"); $sub = $obj->can(’print’); $yes = UNIVERSAL::isa($ref, "HASH");
"UNIVERSAL" is the base class which all bless references will inherit from, see the perlobj manpage
"UNIVERSAL"
provides the following methods
isa ( TYPE )
"isa" returns true if "REF" is blessed into package "TYPE" or inherits from package "TYPE".
"isa" can be called as either a static or object method call.
can ( METHOD )
"can" checks if the object has a method called "METHOD". If it does then a reference to the sub is returned. If it does not then undef is returned.
"can" can be called as either a static or object method call.
VERSION ( [ REQUIRE ] )
"VERSION" will return the value of the variable "$VERSION" in the package the object is blessed into. If "REQUIRE" is given then it will do a comparison and die if the package version is not greater than or equal to "REQUIRE".
"VERSION" can be called as either a static or object method call.
The
"isa" and "can"
methods can also be called as subroutines
UNIVERSAL: :isa ( VAL , TYPE
)
"isa" returns true if one of the following statements is true.
• |
"VAL" is a reference blessed into either package "TYPE" or a package which inherits from package "TYPE". | ||
• |
"VAL" is a reference to a "TYPE" of Perl variable (e.g. ’ HASH ’). | ||
• |
"VAL" is the name of a package that inherits from (or is itself) package "TYPE". |
UNIVERSAL: :can ( VAL , METHOD )
If "VAL" is a blessed reference which has a method called "METHOD", "can" returns a reference to the subroutine. If "VAL" is not a blessed reference, or if it does not have a method "METHOD", undef is returned.
These subroutines should not be imported via "use UNIVERSAL qw(...)". If you want simple local access to them you can do
*isa = \&UNIVERSAL::isa;
to import isa into your package.
UNIVERSAL(3pm) |