Tie::Array(3p) Perl Programmers Reference Guide Tie::Array(3p)NAMETie::Array - base class for tied arrays
SYNOPSIS
package Tie::NewArray;
use Tie::Array;
@ISA = ('Tie::Array');
# mandatory methods
sub TIEARRAY { ... }
sub FETCH { ... }
sub FETCHSIZE { ... }
sub STORE { ... } # mandatory if elements writeable
sub STORESIZE { ... } # mandatory if elements can be added/deleted
sub EXISTS { ... } # mandatory if exists() expected to work
sub DELETE { ... } # mandatory if delete() expected to work
# optional methods - for efficiency
sub CLEAR { ... }
sub PUSH { ... }
sub POP { ... }
sub SHIFT { ... }
sub UNSHIFT { ... }
sub SPLICE { ... }
sub EXTEND { ... }
sub DESTROY { ... }
package Tie::NewStdArray;
use Tie::Array;
@ISA = ('Tie::StdArray');
# all methods provided by default
package main;
$object = tie @somearray,Tie::NewArray;
$object = tie @somearray,Tie::StdArray;
$object = tie @somearray,Tie::NewStdArray;
DESCRIPTION
This module provides methods for array-tying classes. See
perltie for a list of the functions required in order to tie
an array to a package. The basic Tie::Array package provides
stub "DESTROY", and "EXTEND" methods that do nothing, stub
"DELETE" and "EXISTS" methods that croak() if the delete()
or exists() builtins are ever called on the tied array, and
implementations of "PUSH", "POP", "SHIFT", "UNSHIFT",
"SPLICE" and "CLEAR" in terms of basic "FETCH", "STORE",
"FETCHSIZE", "STORESIZE".
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The Tie::StdArray package provides efficient methods
required for tied arrays which are implemented as blessed
references to an "inner" perl array. It inherits from
Tie::Array, and should cause tied arrays to behave exactly
like standard arrays, allowing for selective overloading of
methods.
For developers wishing to write their own tied arrays, the
required methods are briefly defined below. See the perltie
section for more detailed descriptive, as well as example
code:
TIEARRAY classname, LIST
The class method is invoked by the command "tie @array,
classname". Associates an array instance with the speci-
fied class. "LIST" would represent additional arguments
(along the lines of AnyDBM_File and compatriots) needed
to complete the association. The method should return an
object of a class which provides the methods below.
STORE this, index, value
Store datum value into index for the tied array associ-
ated with object this. If this makes the array larger
then class's mapping of "undef" should be returned for
new positions.
FETCH this, index
Retrieve the datum in index for the tied array associ-
ated with object this.
FETCHSIZE this
Returns the total number of items in the tied array
associated with object this. (Equivalent to
"scalar(@array)").
STORESIZE this, count
Sets the total number of items in the tied array associ-
ated with object this to be count. If this makes the
array larger then class's mapping of "undef" should be
returned for new positions. If the array becomes smaller
then entries beyond count should be deleted.
EXTEND this, count
Informative call that array is likely to grow to have
count entries. Can be used to optimize allocation. This
method need do nothing.
EXISTS this, key
Verify that the element at index key exists in the tied
array this.
The Tie::Array implementation is a stub that simply
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croaks.
DELETE this, key
Delete the element at index key from the tied array
this.
The Tie::Array implementation is a stub that simply
croaks.
CLEAR this
Clear (remove, delete, ...) all values from the tied
array associated with object this.
DESTROY this
Normal object destructor method.
PUSH this, LIST
Append elements of LIST to the array.
POP this
Remove last element of the array and return it.
SHIFT this
Remove the first element of the array (shifting other
elements down) and return it.
UNSHIFT this, LIST
Insert LIST elements at the beginning of the array, mov-
ing existing elements up to make room.
SPLICE this, offset, length, LIST
Perform the equivalent of "splice" on the array.
offset is optional and defaults to zero, negative values
count back from the end of the array.
length is optional and defaults to rest of the array.
LIST may be empty.
Returns a list of the original length elements at
offset.
CAVEATS
There is no support at present for tied @ISA. There is a
potential conflict between magic entries needed to notice
setting of @ISA, and those needed to implement 'tie'.
Very little consideration has been given to the behaviour of
tied arrays when $[ is not default value of zero.
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Nick Ing-Simmons <nik@tiuk.ti.com>
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