1Class::MethodMaker::hasUhs(e3r)Contributed Perl DocumentCaltaisosn::MethodMaker::hash(3)
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NAME

6       Class::Method::hash - Create methods for handling a hash value.
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SYNOPSIS

9         use Class::MethodMaker
10           [ hash => [qw/ x /] ];
11
12         $instance->x;                 # empty
13         $instance->x(a => 1, b => 2, c => 3);
14         $instance->x_count == 3;      # true
15         $instance->x = (b => 5, d => 8); # Note this *replaces* the hash,
16                                          # not adds to it
17         $instance->x_index('b') == 5; # true
18         $instance->x_exists('c');     # false
19         $instance->x_exists('d');     # true
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DESCRIPTION

22       Creates methods to handle hash values in an object.  For a component
23       named "x", by default creates methods "x", "x_reset", "x_clear",
24       "x_isset", "x_count", "x_index", "x_keys", "x_values", "x_each",
25       "x_exists", "x_delete", "x_set", "x_get".
26
27       Methods available are:
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29       "*"
30
31       Created by default.  This method returns the list of keys and values
32       stored in the slot (they are returned pairwise, i.e., key, value, key,
33       value; as with perl hashes, no order of keys is guaranteed).  If any
34       arguments are provided to this method, they replace the current hash
35       contents.  In an array context it returns the keys, values as an array
36       and in a scalar context as a hash-reference.  Note that this reference
37       is no longer a direct reference to the storage, in contrast to
38       Class::MethodMaker v1.  This is to protect encapsulation.  See x_ref if
39       you need that functionality (and are prepared to take the associated
40       risk.)
41
42       If a single argument is provided that is an arrayref or hashref, it is
43       expanded and its contents used in place of the existing contents.  This
44       is a more efficient passing mechanism for large numbers of values.
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46       *_reset
47
48       Created by default.  Called without an argument, this resets the
49       component as a whole; deleting any associated storage, and returning
50       the component to its default state.  Normally, this means that *_isset
51       will return false, and * will return undef.  If "-default" is in
52       effect, then the component will be set to the default value, and
53       *_isset will return true.  If "-default_ctor" is in effect, then the
54       default subr will be invoked, and its return value used to set the
55       value of the component, and *_isset will return true.
56
57       If called with arguments, these arguments are treated as indexes into
58       the component, and the individual elements thus referenced are reset
59       (their storage deleted, so that *_isset(n) will return false for
60       appropriate n, except where "-default" or "-default_ctor" are in force,
61       as above).  As with perl arrays, resetting the highest set value
62       implicitly decreases the count (but x_reset(n) never unsets the
63       aggregate itself, even if all the elements are not set).
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65       *_clear
66
67       Created by default.  Empty the component of all elements, but without
68       deleting the storage itself.
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70       If given a list of keys, then the elements that exist indexed by those
71       keys are set to undef (but not deleted).
72
73       Note the very different semantics: "$x->a_clear('b')" sets the value of
74       "b" in component 'a' to undef (if "b") already exists (so
75       "$x->a_isset('b'))" returns true), but "$x->a_clear()" deletes the
76       element "b" from component 'a' (so "$x->a_isset('b'))" returns false).
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78       *_isset
79
80       Created by default.  Whether the component is currently set.  This is
81       different from being defined; initially, the component is not set (and
82       if read, will return undef); it can be set to undef (which is a set
83       value, which also returns undef).  Having been set, the only way to
84       unset the component is with *_reset.
85
86       If a default value is in effect, then *_isset will always return true.
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88       *_isset() tests the component as a whole.  *_isset(a) tests the element
89       indexed by a.  *_isset(a,b) tests the elements indexed by a, b, and
90       returns the logical conjunction (and) of the tests.
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92       *_count
93
94       Created by default.  Returns the number of elements in this component.
95       This is not affected by presence (or lack) of a "default" (or
96       "default_ctor").  Returns "undef" if whole component not set (as per
97       *_isset).
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99       *_index
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101       Created by default.  Takes a list of indices, returns a list of the
102       corresponding values.
103
104       If a default (or a default ctor) is in force, then a lookup by index
105       will vivify & set to the default the respective elements (and therefore
106       the aggregate data-structure also, if it's not already).
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108       *_keys
109
110       Created by default.  The known keys, as a list in list context, as an
111       arrayref in scalar context.
112
113       If you're expecting a count of the keys in scalar context, see *_count.
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115       *_values
116
117       Created by default.  The known values, as a list in list context, as an
118       arrayref in scalar context.
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120       *_each
121
122       Created by default.  The next pair of key, value (as a list) from the
123       hash.
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125       *_exists
126
127       Created by default.  Takes any number of arguments, considers each as a
128       key, and determines whether the key exists in the has.  Returns the
129       logical conjunction (and).
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131       *_delete
132
133       Created by default.  This operates exactly like *_reset, except that
134       calling this with no args does nothing.  This is provided for
135       orthogonality with the Perl "delete" operator, while *_reset is
136       provided for orthogonality with other component types.
137
138       *_set
139
140         %n = $x->h; # (a=>1,b=>2,c=>3) (in some order)
141         $h->h_set(b=>4,d=>7);
142         %n = $h->a; # (a=>1,b=>4,c=>3,d=>7) (in some order)
143
144       Created by default.  Takes a list, treated as pairs of index => value;
145       each given index is set to the corresponding value.  No return.
146
147       If two arguments are given, of which the first is an arrayref, then it
148       is treated as a list of indices of which the second argument (which
149       must also be an arrayref) are the corresponding values.  Thus the
150       following two commands are equivalent:
151
152         $x->a_set(b=>4,d=>7);
153         $x->a_set(['b','d'],[4,7]);
154
155       *_get
156
157       Created by default.  Retrieves the value of the component without
158       setting (ignores any arguments passed).
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162perl v5.34.0                      2021-07-22       Class::MethodMaker::hash(3)
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