ActivePerl Documentation
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Getting Started
Welcome To ActivePerl Release Notes Readme ActivePerl Change Log Install Notes Linux Solaris Windows ActivePerl Components Overview PPM Windows Specifics OLE Browser PerlScript Perl for ISAPI PerlEZ ActivePerl FAQ Introduction Availability & Install Using PPM Docs & Support Windows Specifics Perl for ISAPI Windows 9X/NT/2000 Quirks Web Server Config Web programming Programming Modules & Samples Embedding & Extending Using OLE with Perl Windows Scripting Active Server Pages Windows Script Host Windows Script ComponentsCore Perl Documentation
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UNIVERSAL - base class for ALL classes |
NAME
UNIVERSAL - base class for ALL classes (blessed references)
SUPPORTED PLATFORMS
- Linux
- Solaris
- Windows
SYNOPSIS
$io = $fd->isa("IO::Handle");
$sub = $obj->can('print');
$yes = UNIVERSAL::isa($ref, "HASH");
DESCRIPTION
UNIVERSAL is the base class which all bless references will inherit from,
see the perlobj manpage
UNIVERSAL provides the following methods
- isa ( TYPE )
-
isareturns true ifREFis blessed into packageTYPEor inherits from packageTYPE.isacan be called as either a static or object method call. - can ( METHOD )
-
canchecks if the object has a method calledMETHOD. If it does then a reference to the sub is returned. If it does not then undef is returned.cancan be called as either a static or object method call. - VERSION ( [ REQUIRE ] )
-
VERSIONwill return the value of the variable$VERSIONin the package the object is blessed into. IfREQUIREis given then it will do a comparison and die if the package version is not greater than or equal toREQUIRE.VERSIONcan 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 )
-
isareturns true if one of the following statements is true.-
VALis a reference blessed into either packageTYPEor a package which inherits from packageTYPE. -
VALis a reference to aTYPEof Perl variable (e.g. 'HASH'). -
VALis the name of a package that inherits from (or is itself) packageTYPE.
-
- UNIVERSAL::can ( VAL, METHOD )
-
If
VALis a blessed reference which has a method calledMETHOD,canreturns a reference to the subroutine. IfVALis not a blessed reference, or if it does not have a methodMETHOD, 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.
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UNIVERSAL - base class for ALL classes |