NAME¶
MDOM::Element - The abstract Element class, a base for all source objects
INHERITANCE¶
MDOM::Element is the root of the PDOM tree
DESCRIPTION¶
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.
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.
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.