```{index} single: Tie::Array ``` # Tie::Array base class for tied arrays ## SYNOPSIS ```perl 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](https://perldoc.perl.org/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](https://perldoc.perl.org/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](../AnyDBM_File.md) 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