Tie::Array

Tie::Array(3)          Perl Programmers Reference Guide          Tie::Array(3)



NAME
       Tie::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".

       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 specified 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 associated 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 associated 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 associated 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 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 associ-
           ated 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, moving 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 con-
       flict 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.

AUTHOR
       Nick Ing-Simmons <nik@tiuk.ti.com>



perl v5.8.6                       2001-09-21                     Tie::Array(3)