NAME
PPI::Structure - The base class for Perl braced structures
INHERITANCE
PPI::Structure
isa PPI::Node
isa PPI::ElementDESCRIPTION
PPI::Structure is the root class for all Perl bracing structures. This covers all forms of [ ... ] , { ... } , and ( ... ) brace types, and includes cases where only one half of the pair exist.
The class PPI::Structure itself is full abstract and no objects of that type should actually exist in the tree.
Elements vs Children
A PPI::Structure has an unusual existence. Unlike a PPI::Document or PPI::Statement, which both simply contain other elements, a structure both contains and consists of content.
That is, the brace tokens are not considered to be "children" of the structure, but are part of it.
In practice, this will mean that while the ->elements and ->tokens methods (and related) will return a list with the brace tokens at either end, the ->children method explicitly will not return the brace.
STRUCTURE CLASSES
Excluding the transient PPI::Structure::Unknown that exists briefly inside the parser, there are eight types of structure.
PPI::Structure::List
This covers all round braces used for function arguments, in foreach loops, literal lists, and braces used for precedence-ordering purposes.
PPI::Structure::For
Although not used for the foreach loop list, this is used for the special case of the round-brace three-part semicolon-separated for loop expression (the traditional C style for loop).
PPI::Structure::Given
This is for the expression being matched in switch statements.
PPI::Structure::When
This is for the matching expression in "when" statements.
PPI::Structure::Condition
This round-brace structure covers boolean conditional braces, such as for if and while blocks.
PPI::Structure::Block
This curly-brace and common structure is used for all form of code blocks. This includes those for if, do and similar, as well as grep, map, sort, sub and (labelled or anonymous) scoping blocks.
PPI::Structure::Constructor
This class covers brace structures used for the construction of anonymous ARRAY and HASH references.
PPI::Structure::Subscript
This class covers square-braces and curly-braces used after a -> pointer to access the subscript of an ARRAY or HASH.
METHODS
PPI::Structure itself has very few methods. Most of the time, you will be working with the more generic PPI::Element or PPI::Node methods, or one of the methods that are subclass-specific.
start
For lack of better terminology (like "open" and "close") that has not already in use for some other more important purpose, the two individual braces for the structure are known within PPI as the "start" and "finish" braces (at least for method purposes).
The start method returns the start brace for the structure (i.e. the opening brace).
Returns the brace as a PPI::Token::Structure or undef if the structure does not have a starting brace.
Under normal parsing circumstances this should never occur, but may happen due to manipulation of the PDOM tree.
finish
The finish method returns the finish brace for the structure (i.e. the closing brace).
Returns the brace as a PPI::Token::Structure or undef if the structure does not have a finishing brace. This can be quite common if the document is not complete (for example, from an editor where the user may be halfway through typeing a subroutine).
braces
The braces method is a utility method which returns the brace type, regardless of whether both or just one of the braces is defined.
Returns one of the three strings '[]', '{}', or '()', or undef on error (primarily not having a start brace, as mentioned above).
complete
The complete method is a convenience method that returns true if the both braces are defined for the structure, or false if only one brace is defined.
Unlike the top level complete method which checks for completeness in depth, the structure complete method ONLY confirms completeness for the braces, and does not recurse downwards.
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.