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Manual Reference Pages  -  CLASS::METHODMAKER::HASH (3)

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NAME

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

CONTENTS

SYNOPSIS



  use Class::MethodMaker
    [ hash => [qw/ x /] ];

  $instance->x;                 # empty
  $instance->x(a => 1, b => 2, c => 3);
  $instance->x_count == 3;      # true
  $instance->x = (b => 5, d => 8); # Note this *replaces* the hash,
                                   # not adds to it
  $instance->x_index(b) == 5; # true
  $instance->x_exists(c);     # false
  $instance->x_exists(d);     # true



DESCRIPTION

Creates methods to handle hash values in an object. For a component named x, by default creates methods x, x_reset, x_clear, x_isset, x_count, x_index, x_keys, x_values, x_each, x_exists, x_delete, x_set, x_get.

Methods available are:

*

Created by default. This method returns the list of keys and values stored in the slot (they are returned pairwise, i.e., key, value, key, value; as with perl hashes, no order of keys is guaranteed). If any arguments are provided to this method, they <B>replaceB> the current hash contents. In an array context it returns the keys, values as an array and in a scalar context as a hash-reference. Note that this reference is no longer a direct reference to the storage, in contrast to Class::MethodMaker v1. This is to protect encapsulation. See x_ref if you need that functionality (and are prepared to take the associated risk.)

If a single argument is provided that is an arrayref or hashref, it is expanded and its contents used in place of the existing contents. This is a more efficient passing mechanism for large numbers of values.

*_reset

Created by default. Called without an argument, this resets the component as a whole; deleting any associated storage, and returning the component to its default state. Normally, this means that *_isset will return false, and * will return undef. If -default is in effect, then the component will be set to the default value, and *_isset will return true. If -default_ctor is in effect, then the default subr will be invoked, and its return value used to set the value of the component, and *_isset will return true.

If called with arguments, these arguments are treated as indexes into the component, and the individual elements thus referenced are reset (their storage deleted, so that *_isset(n) will return false for appropriate n, except where -default or -default_ctor are in force, as above). As with perl arrays, resetting the highest set value implicitly decreases the count (but x_reset(n) never unsets the aggregate itself, even if all the elements are not set).

*_clear

Created by default. Empty the component of all elements, but without deleting the storage itself.

If given a list of keys, then the elements that exist indexed by those keys are set to undef (but not deleted).

Note the very different semantics: $x->a_clear(b) sets the value of b in component ’a’ to undef (if b) already exists (so $x->a_isset(b)) returns true), but $x->a_clear() deletes the element b from component ’a’ (so $x->a_isset(b)) returns false).

*_isset

Created by default. Whether the component is currently set. This is different from being defined; initially, the component is not set (and if read, will return undef); it can be set to undef (which is a set value, which also returns undef). Having been set, the only way to unset the component is with *_reset.

If a default value is in effect, then *_isset will always return true.

*_isset() tests the component as a whole. *_isset(a) tests the element indexed by a. *_isset(a,b) tests the elements indexed by a, b, and returns the logical conjunction (and) of the tests.

*_count

Created by default. Returns the number of elements in this component. This is not affected by presence (or lack) of a default (or default_ctor). Returns undef if whole component not set (as per *_isset).

*_index

Created by default. Takes a list of indices, returns a list of the corresponding values.

If a default (or a default ctor) is in force, then a lookup by index will vivify & set to the default the respective elements (and therefore the aggregate data-structure also, if it’s not already).

*_keys

Created by default. The known keys, as a list in list context, as an arrayref in scalar context.

If you’re expecting a count of the keys in scalar context, see *_count.

*_values

Created by default. The known values, as a list in list context, as an arrayref in scalar context.

*_each

Created by default. The next pair of key, value (as a list) from the hash.

*_exists

Created by default. Takes any number of arguments, considers each as a key, and determines whether the key exists in the has. Returns the logical conjunction (and).

*_delete

Created by default. This operates exactly like *_reset, except that calling this with no args does nothing. This is provided for orthogonality with the Perl delete operator, while *_reset is provided for orthogonality with other component types.

*_set



  %n = $x->h; # (a=>1,b=>2,c=>3) (in some order)
  $h->h_set(b=>4,d=>7);
  %n = $h->a; # (a=>1,b=>4,c=>3,d=>7) (in some order)



Created by default. Takes a list, treated as pairs of index => value; each given index is set to the corresponding value. No return.

If two arguments are given, of which the first is an arrayref, then it is treated as a list of indices of which the second argument (which must also be an arrayref) are the corresponding values. Thus the following two commands are equivalent:



  $x->a_set(b=>4,d=>7);
  $x->a_set([b,d],[4,7]);



*_get

Created by default. Retrieves the value of the component without setting (ignores any arguments passed).

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perl v5.20.3 CLASS::METHODMAKER::HASH (3) 2016-03-17

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