perl-Safe-Isa

Call isa, can, does and DOES safely on things that may not be objects

How many times have you found yourself writing: if ($obj->isa('Something')) { and then shortly afterwards cursing and changing it to: if (Scalar::Util::blessed($obj) and $obj->isa('Something')) { Right. That's why this module exists. Since perl allows us to provide a subroutine reference or a method name to the -> operator when used as a method call, and a subroutine doesn't require the invocant to actually be an object, we can create safe versions of isa, can and friends by using a subroutine reference that only tries to call the method if it's used on an object. So: my $isa_Foo = $maybe_an_object->$_call_if_object(isa => 'Foo'); is equivalent to my $isa_Foo = do { if (Scalar::Util::blessed($maybe_an_object)) { $maybe_an_object->isa('Foo'); } else { undef; } }; Note that we don't handle trying class names, because many things are valid class names that you might not want to treat as one (like say "Matt") - the 'is_module_name' function from Module::Runtime is a good way to check for something you might be able to call methods on if you want to do that. We are careful to make sure that scalar/list context is preserved for the method that is eventually called.