4 use warnings FATAL => 'all';
5 use Scalar::Util qw(blessed);
6 use Exporter 5.57 qw(import);
8 our $VERSION = '1.000005';
10 our @EXPORT = qw($_call_if_object $_isa $_can $_does $_DOES);
12 our $_call_if_object = sub {
13 my ($obj, $method) = (shift, shift);
14 # This is intentionally a truth test, not a defined test, otherwise
15 # we gratuitously break modules like Scalar::Defer, which would be
17 return unless blessed($obj);
18 return $obj->$method(@_);
21 our ($_isa, $_can, $_does, $_DOES) = map {
23 sub { my $obj = shift; $obj->$_call_if_object($method => @_) }
24 } qw(isa can does DOES);
28 Safe::Isa - Call isa, can, does and DOES safely on things that may not be objects
35 { package Foo; sub new { bless({}, $_[0]) } }
36 { package Bar; our @ISA = qw(Foo); sub bar { 1 } }
44 $foo->isa('Foo'); # true
45 $bar->isa('Foo'); # true
46 $blam->isa('Foo'); # BOOM
48 $foo->can('bar'); # false
49 $bar->can('bar'); # true
50 $blam->can('bar'); # BOOM
56 $foo->$_isa('Foo'); # true
57 $bar->$_isa('Foo'); # true
58 $blam->$_isa('Foo'); # false, no boom today
60 $foo->$_can('bar'); # false
61 $bar->$_can('bar'); # true
62 $blam->$_can('bar'); # false, no boom today
66 $maybe_an_object->$_does('RoleName'); # true or false, no boom today
67 $maybe_an_object->$_DOES('RoleName'); # true or false, no boom today
69 And just in case we missed a method:
71 $maybe_an_object->$_call_if_object(name => @args);
73 Or to re-use a previous example for purposes of explication:
75 $foo->$_call_if_object(isa => 'Foo'); # true
76 $bar->$_call_if_object(isa => 'Foo'); # true
77 $blam->$_call_if_object(isa => 'Foo'); # false, no boom today
81 How many times have you found yourself writing:
83 if ($obj->isa('Something')) {
85 and then shortly afterwards cursing and changing it to:
87 if (Scalar::Util::blessed($obj) and $obj->isa('Something')) {
89 Right. That's why this module exists.
91 Since perl allows us to provide a subroutine reference or a method name to
92 the -> operator when used as a method call, and a subroutine doesn't require
93 the invocant to actually be an object, we can create safe versions of isa,
94 can and friends by using a subroutine reference that only tries to call the
95 method if it's used on an object. So:
97 my $isa_Foo = $maybe_an_object->$_call_if_object(isa => 'Foo');
102 if (Scalar::Util::blessed($maybe_an_object)) {
103 $maybe_an_object->isa('Foo');
109 Note that we don't handle trying class names, because many things are valid
110 class names that you might not want to treat as one (like say "Matt") - the
111 C<is_module_name> function from L<Module::Runtime> is a good way to check for
112 something you might be able to call methods on if you want to do that.
118 $maybe_an_object->$_isa('Foo');
120 If called on an object, calls C<isa> on it and returns the result, otherwise
125 $maybe_an_object->$_can('Foo');
127 If called on an object, calls C<can> on it and returns the result, otherwise
132 $maybe_an_object->$_does('Foo');
134 If called on an object, calls C<does> on it and returns the result, otherwise
139 $maybe_an_object->$_DOES('Foo');
141 If called on an object, calls C<DOES> on it and returns the result, otherwise
144 =head2 $_call_if_object
146 $maybe_an_object->$_call_if_object(method_name => @args);
148 If called on an object, calls C<method_name> on it and returns the result,
149 otherwise returns nothing.
153 I gave a lightning talk on this module (and L<curry> and L<Import::Into>) at
154 L<YAPC::NA 2013|https://www.youtube.com/watch?v=wFXWV2yY7gE&t=46m05s>.
158 mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
162 None yet. Well volunteered? :)
166 Copyright (c) 2012 the Safe::Isa L</AUTHOR> and L</CONTRIBUTORS>
171 This library is free software and may be distributed under the same terms