NAME
MDOM::Element - The abstract Element class, a base for all source objects
INHERITANCE
MDOM::Element is the root of the PDOM treeDESCRIPTION
The abstract MDOM::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 MDOM::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.
lineno
Accessor for current line number.
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 MDOM::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 MDOM::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 MDOM::Token::HereDoc.
The MDOM::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 MDOM::Node abstract class, a subclass of MDOM::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.
statement
For a MDOM::Element that is contained (at some depth) within a MDOM::Statment, the statement method will return the first parent Statement object lexically 'above' the Element.
Returns a MDOM::Statement object, which may be the same Element if the Element is itself a MDOM::Statement object.
Returns false if the Element is not within a Statement and is not itself a Statement.
top
For a MDOM::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 MDOM::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 MDOM::Document object, the document method will return the top-level Document for the Element.
Returns the MDOM::Document for this Element, or false if the Element is not contained within a Document.
next_sibling
All MDOM::Node objects (specifically, our parent Node) contain a number of MDOM::Element objects. The next_sibling method returns the MDOM::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 MDOM::Element object.
Returns a MDOM::Element object, or false if there is no 'next' significant sibling.
previous_sibling
All MDOM::Node objects (specifically, our parent Node) contain a number of MDOM::Element objects. The previous_sibling method returns the Element immediately before the current one, or false if there is no 'previous' MDOM::Element object.
sprevious_sibling
As per the other 's' methods, the sprevious_sibling method returns the previous significant sibling of the MDOM::Element object.
Returns a MDOM::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 MDOM::Token object within or equal to this one.
That is, if called on a MDOM::Node subclass, it will descend until it finds a MDOM::Token. If called on a MDOM::Token object, it will return the same object.
Returns a MDOM::Token object, or dies on error (which should be extremely rare and only occur if an illegal empty MDOM::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 MDOM::Token object within or equal to this one.
That is, if called on a MDOM::Node subclass, it will descend until it finds a MDOM::Token. If called on a MDOM::Token object, it will return the itself.
Returns a MDOM::Token object, or dies on error (which should be extremely rare and only occur if an illegal empty MDOM::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 MDOM::Token object that is immediately after the current Element, even if it is not within the same parent MDOM::Node as the one for which the method is being called.
Note that this is not defined as a MDOM::Token-specific method, because it can be useful to find the next token that is after, say, a MDOM::Statement, although obviously it would be useless to want the next token after a MDOM::Document.
Returns a MDOM::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 MDOM::Token object that is immediately before the current Element, even if it is not within the same parent MDOM::Node as this one.
Note that this is not defined as a MDOM::Token-only method, because it can be useful to find the token is before, say, a MDOM::Statement, although obviously it would be useless to want the next token before a MDOM::Document.
Returns a MDOM::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 MDOM::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 MDOM::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 MDOM::Element object as a parameter.
insert_after @Elements
The insert_after method allows you to insert lexical perl content, in the form of MDOM::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 MDOM::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 MDOM::Element object as a parameter.
remove
For a given MDOM::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 MDOM::Element, the remove 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.
location
If the Element exists within a MDOM::Document that has indexed the Element locations using MDOM::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 three-element array in the form [ $line, $rowchar, $col ]. The values are in a human format, with the first character of the file located at [ 1, 1, 1 ].
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.
Returns undef on error, or if the MDOM::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 - 2006 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.