1UNIVERSAL::isa(3) User Contributed Perl Documentation UNIVERSAL::isa(3)
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6 UNIVERSAL::isa - Attempt to recover from people calling UNIVERSAL::isa
7 as a function
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10 version 1.20171012
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13 # from the shell
14 echo 'export PERL5OPT=-MUNIVERSAL::isa' >> /etc/profile
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16 # within your program
17 use UNIVERSAL::isa;
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19 # enable warnings for all dodgy uses of UNIVERSAL::isa
20 use UNIVERSAL::isa 'verbose';
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23 Whenever you use "isa" in UNIVERSAL as a function, a kitten using
24 Test::MockObject dies. Normally, the kittens would be helpless, but if
25 they use UNIVERSAL::isa (the module whose docs you are reading), the
26 kittens can live long and prosper.
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28 This module replaces "UNIVERSAL::isa" with a version that makes sure
29 that, when called as a function on objects which override "isa", "isa"
30 will call the appropriate method on those objects
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32 In all other cases, the real "UNIVERSAL::isa" gets called directly.
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34 NOTE: You should use this module only for debugging purposes. It does
35 not belong as a dependency in running code.
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38 original_isa
39 This sub contains the definition of the original "UNIVERSAL::isa"
40 definition, in case you need it.
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43 If the lexical warnings pragma is available, this module will emit a
44 warning for each naughty invocation of "UNIVERSAL::isa". Silence these
45 warnings by saying:
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47 no warnings 'UNIVERSAL::isa';
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49 in the lexical scope of the naughty code.
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51 After version 1.00, warnings only appear when naughty code calls
52 UNIVERSAL::isa() as a function on an invocant for which there is an
53 overridden isa(). These are really truly active bugs, and you should
54 fix them rather than relying on this module to find them.
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56 To get warnings for all potentially dangerous uses of UNIVERSAL::isa()
57 as a function, not a method (that is, for all uses of the method as a
58 function, which are latent bugs, if not bugs that will break your code
59 as it exists now), pass the "verbose" flag when using the module. This
60 can generate many extra warnings, but they're more specific as to the
61 actual wrong practice and they usually suggest proper fixes.
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64 Perl::Critic::Policy::BuiltinFunctions::ProhibitUniversalIsa
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66 UNIVERSAL::can for another discussion of the problem at hand.
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68 Test::MockObject for one example of a module that really needs to
69 override "isa()".
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71 Any decent explanation of OO to understand why calling methods as
72 functions is a staggeringly bad idea.
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75 Bugs may be submitted through the RT bug tracker
76 <https://rt.cpan.org/Public/Dist/Display.html?Name=UNIVERSAL-isa> (or
77 bug-UNIVERSAL-isa@rt.cpan.org <mailto:bug-UNIVERSAL-isa@rt.cpan.org>).
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80 · Audrey Tang <cpan@audreyt.org>
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82 · chromatic <chromatic@wgz.org>
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84 · יובל קוג'מן (Yuval Kogman) <nothingmuch@woobling.org>
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87 · Karen Etheridge <ether@cpan.org>
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89 · Graham Knop <haarg@haarg.org>
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91 · Ricardo Signes <rjbs@cpan.org>
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94 This software is copyright (c) 2011 by chromatic@wgz.org.
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96 This is free software; you can redistribute it and/or modify it under
97 the same terms as the Perl 5 programming language system itself.
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101perl v5.28.0 2018-07-15 UNIVERSAL::isa(3)