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

# 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 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, 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 conflict between magic entries needed to notice setting of @ISA, and those needed to implement 'tie'.

# AUTHOR

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

2019-02-13 | perl v5.40.1