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.IX Title "Perl::Critic::Policy::BuiltinFunctions::ProhibitUniversalIsa 3pm"
.TH Perl::Critic::Policy::BuiltinFunctions::ProhibitUniversalIsa 3pm 2023-07-26 "perl v5.38.0" "User Contributed Perl Documentation"
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.SH NAME
Perl::Critic::Policy::BuiltinFunctions::ProhibitUniversalIsa \- Write "eval { $foo\->isa($pkg) }" instead of "UNIVERSAL::isa($foo, $pkg)".
.SH AFFILIATION
.IX Header "AFFILIATION"
This Policy is part of the core Perl::Critic
distribution.
.SH DESCRIPTION
.IX Header "DESCRIPTION"
.Vb 2
\&    print UNIVERSAL::isa($obj, \*(AqFoo::Bar\*(Aq) ? \*(Aqyes\*(Aq : \*(Aqno\*(Aq;  #not ok
\&    print eval { $obj\->isa(\*(AqFoo::Bar\*(Aq) } ? \*(Aqyes\*(Aq : \*(Aqno\*(Aq;    #ok
.Ve
.PP
As of Perl 5.9.3, the use of \f(CW\*(C`UNIVERSAL::isa\*(C'\fR as a function has been
deprecated and the method form is preferred instead.  Formerly, the
functional form was recommended because it gave valid results even
when the object was \f(CW\*(C`undef\*(C'\fR or an unblessed scalar.  However, the
functional form makes it impossible for packages to override \f(CWisa()\fR,
a technique which is crucial for implementing mock objects and some
facades.
.PP
Another alternative to UNIVERSAL::isa is the \f(CW\*(C`_INSTANCE\*(C'\fR method of
Param::Util, which is faster.
.PP
See the CPAN module UNIVERSAL::isa for an incendiary
discussion of this topic.
.SH CONFIGURATION
.IX Header "CONFIGURATION"
This Policy is not configurable except for the standard options.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Perl::Critic::Policy::BuiltinFunctions::ProhibitUniversalCan
.SH AUTHOR
.IX Header "AUTHOR"
Chris Dolan <cdolan@cpan.org>
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright (c) 2006\-2011 Chris Dolan.
.PP
This program is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.  The full text of this license
can be found in the LICENSE file included with this module.