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def3c102 |
1 | package UNIVERSAL; |
2 | |
3 | require Exporter; |
4 | @ISA = qw(Exporter); |
5 | @EXPORT_OK = qw(isa); |
6 | |
7 | 1; |
8 | __END__ |
9 | |
10 | =head1 NAME |
11 | |
12 | UNIVERSAL - base class for ALL classes (blessed references) |
13 | |
14 | =head1 SYNOPSIS |
15 | |
16 | use UNIVERSAL qw(isa); |
17 | |
18 | $yes = isa($ref, "HASH"); |
19 | $io = $fd->isa("IO::Handle"); |
20 | $sub = $obj->can('print'); |
21 | |
22 | =head1 DESCRIPTION |
23 | |
24 | C<UNIVERSAL> is the base class which all bless references will inherit from, |
25 | see L<perlobj> |
26 | |
27 | C<UNIVERSAL> provides the following methods |
28 | |
29 | =over 4 |
30 | |
31 | =item isa ( TYPE ) |
32 | |
33 | C<isa> returns I<true> if C<REF> is blessed into package C<TYPE> |
34 | or inherits from package C<TYPE>. |
35 | |
36 | C<isa> can be called as either a static or object method call. |
37 | |
38 | =item can ( METHOD ) |
39 | |
40 | C<can> checks if the object has a method called C<METHOD>. If it does |
41 | then a reference to the sub is returned. If it does not the I<undef> |
42 | is returned. |
43 | |
44 | C<can> can be called as either a static or object method call. |
45 | |
46 | =item VERSION ( [ REQUIRE ] ) |
47 | |
48 | C<VERSION> will return the value of the variable C<$VERSION> in the |
49 | package the object is blessed into. If C<REQUIRE> is given then |
50 | it will do a comparison and die if the package version is not |
51 | greater than or equal to C<REQUIRE>. |
52 | |
53 | C<VERSION> can be called as either a static or object method call. |
54 | |
55 | =back |
56 | |
57 | C<UNIVERSAL> also optionally exports the following subroutines |
58 | |
59 | =over 4 |
60 | |
61 | =item isa ( REF, TYPE ) |
62 | |
63 | C<isa> returns I<true> if the first argument is a reference and either |
64 | of the following statements is true. |
65 | |
66 | =over 8 |
67 | |
68 | =item |
69 | |
70 | C<REF> is a blessed reference and is blessed into package C<TYPE> |
71 | or inherits from package C<TYPE> |
72 | |
73 | =item |
74 | |
75 | C<REF> is a reference to a C<TYPE> of perl variable (er 'HASH') |
76 | |
77 | =back |
78 | |
79 | =back |
80 | |
81 | =cut |