PPI::Element(3p)

NAME
PPI::Element - The abstract Element class, a base for all source objects

INHERITANCE
  PPI::Element is the root of the PDOM tree

DESCRIPTION
The abstract "PPI::Element" serves as a base class for all source-related objects, from a single whitespace token to an entire document. It provides a basic set of methods to provide a common interface and basic implementations.

METHODS

  significant
Because we treat whitespace and other non-code items as Tokens (in order to be able to "round trip" the PPI::Document back to a file) the "significant" method allows us to distinguish between tokens that form a part of the code, and tokens that aren't significant, such as whitespace, POD, or the portion of a file after (and including) the "__END__" token.

Returns true if the Element is significant, or false it not.

  class
The "class" method is provided as a convenience, and really does nothing more than returning ref($self). However, some people have found that they appreciate the laziness of "$Foo->class eq 'whatever'", so I have caved to popular demand and included it.

Returns the class of the Element as a string

  tokens
The "tokens" method returns a list of PPI::Token objects for the Element, essentially getting back that part of the document as if it had not been lexed.

This also means there are no Statements and no Structures in the list, just the Token classes.

  content
For any "PPI::Element", the "content" method will reconstitute the base code for it as a single string. This method is also the method used for overloading stringification. When an Element is used in a double-quoted string for example, this is the method that is called.

WARNING:

You should be aware that because of the way that here-docs are handled, any here-doc content is not included in "content", and as such you should not eval or execute the result if it contains any PPI::Token::HereDoc.

The PPI::Document method "serialize" should be used to stringify a PDOM document into something that can be executed as expected.

Returns the basic code as a string (excluding here-doc content).

  parent
Elements themselves are not intended to contain other Elements, that is left to the PPI::Node abstract class, a subclass of "PPI::Element". However, all Elements can be contained within a parent Node.

If an Element is within a parent Node, the "parent" method returns the Node.

  descendant_of $element
Answers whether a "PPI::Element" is contained within another one.

"PPI::Element"s are considered to be descendants of themselves.

  ancestor_of $element
Answers whether a "PPI::Element" is contains another one.

"PPI::Element"s are considered to be ancestors of themselves.

  statement
For a "PPI::Element" that is contained (at some depth) within a PPI::Statement, the "statement" method will return the first parent Statement object lexically 'above' the Element.

Returns a PPI::Statement object, which may be the same Element if the Element is itself a PPI::Statement object.

Returns false if the Element is not within a Statement and is not itself a Statement.

  top
For a "PPI::Element" that is contained within a PDOM tree, the "top" method will return the top-level Node in the tree. Most of the time this should be a PPI::Document object, however this will not always be so. For example, if a subroutine has been removed from its Document, to be moved to another Document.

Returns the top-most PDOM object, which may be the same Element, if it is not within any parent PDOM object.

  document
For an Element that is contained within a PPI::Document object, the "document" method will return the top-level Document for the Element.

Returns the PPI::Document for this Element, or false if the Element is not contained within a Document.

  next_sibling
All PPI::Node objects (specifically, our parent Node) contain a number of "PPI::Element" objects. The "next_sibling" method returns the "PPI::Element" immediately after the current one, or false if there is no next sibling.

  snext_sibling
As per the other 's' methods, the "snext_sibling" method returns the next significant sibling of the "PPI::Element" object.

Returns a "PPI::Element" object, or false if there is no 'next' significant sibling.

  previous_sibling
All PPI::Node objects (specifically, our parent Node) contain a number of "PPI::Element" objects. The "previous_sibling" method returns the Element immediately before the current one, or false if there is no 'previous' "PPI::Element" object.

  sprevious_sibling
As per the other 's' methods, the "sprevious_sibling" method returns the previous significant sibling of the "PPI::Element" object.

Returns a "PPI::Element" object, or false if there is no 'previous' significant sibling.

  first_token
As a support method for higher-order algorithms that deal specifically with tokens and actual Perl content, the "first_token" method finds the first PPI::Token object within or equal to this one.

That is, if called on a PPI::Node subclass, it will descend until it finds a PPI::Token. If called on a PPI::Token object, it will return the same object.

Returns a PPI::Token object, or dies on error (which should be extremely rare and only occur if an illegal empty PPI::Statement exists below the current Element somewhere.)

  last_token
As a support method for higher-order algorithms that deal specifically with tokens and actual Perl content, the "last_token" method finds the last PPI::Token object within or equal to this one.

That is, if called on a PPI::Node subclass, it will descend until it finds a PPI::Token. If called on a PPI::Token object, it will return the itself.

Returns a PPI::Token object, or dies on error (which should be extremely rare and only occur if an illegal empty PPI::Statement exists below the current Element somewhere.)

  next_token
As a support method for higher-order algorithms that deal specifically with tokens and actual Perl content, the "next_token" method finds the PPI::Token object that is immediately after the current Element, even if it is not within the same parent PPI::Node as the one for which the method is being called.

Note that this is not defined as a PPI::Token-specific method, because it can be useful to find the next token that is after, say, a PPI::Statement, although obviously it would be useless to want the next token after a PPI::Document.

Returns a PPI::Token object, or false if there are no more tokens after the Element.

  previous_token
As a support method for higher-order algorithms that deal specifically with tokens and actual Perl content, the "previous_token" method finds the PPI::Token object that is immediately before the current Element, even if it is not within the same parent PPI::Node as this one.

Note that this is not defined as a PPI::Token-only method, because it can be useful to find the token is before, say, a PPI::Statement, although obviously it would be useless to want the next token before a PPI::Document.

Returns a PPI::Token object, or false if there are no more tokens before the "Element".

  clone
As per the Clone module, the "clone" method makes a perfect copy of an Element object. In the generic case, the implementation is done using the Clone module's mechanism itself. In higher-order cases, such as for Nodes, there is more work involved to keep the parent-child links intact.

  insert_before @Elements
The "insert_before" method allows you to insert lexical perl content, in the form of "PPI::Element" objects, before the calling "Element". You need to be very careful when modifying perl code, as it's easy to break things.

In its initial incarnation, this method allows you to insert a single Element, and will perform some basic checking to prevent you inserting something that would be structurally wrong (in PDOM terms).

In future, this method may be enhanced to allow the insertion of multiple Elements, inline-parsed code strings or PPI::Document::Fragment objects.

Returns true if the Element was inserted, false if it can not be inserted, or "undef" if you do not provide a "PPI::Element" object as a parameter.

  insert_after @Elements
The "insert_after" method allows you to insert lexical perl content, in the form of "PPI::Element" objects, after the calling "Element". You need to be very careful when modifying perl code, as it's easy to break things.

In its initial incarnation, this method allows you to insert a single Element, and will perform some basic checking to prevent you inserting something that would be structurally wrong (in PDOM terms).

In future, this method may be enhanced to allow the insertion of multiple Elements, inline-parsed code strings or PPI::Document::Fragment objects.

Returns true if the Element was inserted, false if it can not be inserted, or "undef" if you do not provide a "PPI::Element" object as a parameter.

  remove
For a given "PPI::Element", the "remove" method will remove it from its parent intact, along with all of its children.

Returns the "Element" itself as a convenience, or "undef" if an error occurs while trying to remove the "Element".

  delete
For a given "PPI::Element", the "delete" method will remove it from its parent, immediately deleting the "Element" and all of its children (if it has any).

Returns true if the "Element" was successfully deleted, or "undef" if an error occurs while trying to remove the "Element".

  replace $Element
Although some higher level class support more exotic forms of replace, at the basic level the "replace" method takes a single "Element" as an argument and replaces the current "Element" with it.

To prevent accidental damage to code, in this initial implementation the replacement element must be of the same class (or a subclass) as the one being replaced.

If successful, returns the replace element. Otherwise, returns "undef".

  location
If the Element exists within a PPI::Document that has indexed the Element locations using "PPI::Document::index_locations", the "location" method will return the location of the first character of the Element within the Document.

Returns the location as a reference to a five-element array in the form "[ $line, $rowchar, $col, $logical_line, $logical_file_name ]". The values are in a human format, with the first character of the file located at "[ 1, 1, 1, ?, 'something' ]".

The second and third numbers are similar, except that the second is the literal horizontal character, and the third is the visual column, taking into account tabbing (see "tab_width [ $width ]" in PPI::Document).

The fourth number is the line number, taking into account any "#line" directives. The fifth element is the name of the file that the element was found in, if available, taking into account any "#line" directives.

Returns "undef" on error, or if the PPI::Document object has not been indexed.

  line_number
If the Element exists within a PPI::Document that has indexed the Element locations using "PPI::Document::index_locations", the "line_number" method will return the line number of the first character of the Element within the Document.

Returns "undef" on error, or if the PPI::Document object has not been indexed.

  column_number
If the Element exists within a PPI::Document that has indexed the Element locations using "PPI::Document::index_locations", the "column_number" method will return the column number of the first character of the Element within the Document.

Returns "undef" on error, or if the PPI::Document object has not been indexed.

  visual_column_number
If the Element exists within a PPI::Document that has indexed the Element locations using "PPI::Document::index_locations", the "visual_column_number" method will return the visual column number of the first character of the Element within the Document, according to the value of "tab_width [ $width ]" in PPI::Document.

Returns "undef" on error, or if the PPI::Document object has not been indexed.

  logical_line_number
If the Element exists within a PPI::Document that has indexed the Element locations using "PPI::Document::index_locations", the "logical_line_number" method will return the line number of the first character of the Element within the Document, taking into account any "#line" directives.

Returns "undef" on error, or if the PPI::Document object has not been indexed.

  logical_filename
If the Element exists within a PPI::Document that has indexed the Element locations using "PPI::Document::index_locations", the "logical_filename" method will return the logical file name containing the first character of the Element within the Document, taking into account any "#line" directives.

Returns "undef" on error, or if the PPI::Document object has not been indexed.

TO DO
It would be nice if "location" could be used in an ad-hoc manner. That is, if called on an Element within a Document that has not been indexed, it will do a one-off calculation to find the location. It might be very painful if someone started using it a lot, without remembering to index the document, but it would be handy for things that are only likely to use it once, such as error handlers.

SUPPORT
See the support section in the main module.

AUTHOR
Adam Kennedy <adamk@cpan.org>

COPYRIGHT
Copyright 2001 - 2011 Adam Kennedy.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

The full text of the license can be found in the LICENSE file included with this module.