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.\"
.IX Title "PPI::Transform 3pm"
.TH PPI::Transform 3pm "2019-07-21" "perl v5.28.1" "User Contributed Perl Documentation"
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.SH "NAME"
PPI::Transform \- Abstract base class for document transformation classes
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\f(CW\*(C`PPI::Transform\*(C'\fR provides an \s-1API\s0 for the creation of classes and objects
that modify or transform \s-1PPI\s0 documents.
.SH "METHODS"
.IX Header "METHODS"
.SS "new"
.IX Subsection "new"
.Vb 4
\&  my $transform = PPI::Transform\->new(
\&      param1 => \*(Aqvalue1\*(Aq,
\&      param2 => \*(Aqvalue2\*(Aq,
\&  );
.Ve
.PP
The \f(CW\*(C`new\*(C'\fR constructor creates a new object for your \f(CW\*(C`PPI::Transform\*(C'\fR
subclass. A default constructor is provided for you which takes no params
and creates a basic, empty, object.
.PP
If you wish to have your transform constructor take params, these \fBmust\fR
be in the form of a list of key/value pairs.
.PP
Returns a new \f(CW\*(C`PPI::Transform\*(C'\fR\-compatible object, or returns
\&\f(CW\*(C`undef\*(C'\fR on error.
.SS "document"
.IX Subsection "document"
The \f(CW\*(C`document\*(C'\fR method should be implemented by each subclass, and
takes a single argument of a PPI::Document object, modifying it
\&\fBin place\fR as appropriate for the particular transform class.
.PP
That's right, this method \fBwill not clone\fR and \fBshould not clone\fR
the document object. If you do not want the original to be modified,
you need to clone it yourself before passing it in.
.PP
Returns the numbers of changes made to the document. If the transform
is unable to track the quantity (including the situation where it cannot
tell \fB\s-1IF\s0\fR it made a change) it should return 1. Returns zero if no
changes were made to the document, or \f(CW\*(C`undef\*(C'\fR if an error occurs.
.PP
By default this error is likely to only mean that you passed in something
that wasn't a PPI::Document, but may include additional errors
depending on the subclass.
.SS "apply"
.IX Subsection "apply"
The \f(CW\*(C`apply\*(C'\fR method is used to apply the transform to something. The
argument must be a PPI::Document, or something which can be turned
into one and then be written back to again.
.PP
Currently, this list is limited to a \f(CW\*(C`SCALAR\*(C'\fR reference, although a
handler registration process is available for you to add support for
additional types of object should you wish (see the source for this module).
.PP
Returns true if the transform was applied, false if there is an error in the
transform process, or may die if there is a critical error in the apply
handler.
.SS "file"
.IX Subsection "file"
.Vb 2
\&  # Read from one file and write to another
\&  $transform\->file( \*(AqInput.pm\*(Aq => \*(AqOutput.pm\*(Aq );
\&  
\&  # Change a file in place
\&  $transform\->file( \*(AqChange.pm\*(Aq );
.Ve
.PP
The \f(CW\*(C`file\*(C'\fR method modifies a Perl document by filename. If passed a single
parameter, it modifies the file in-place. If provided a second parameter,
it will attempt to save the modified file to the alternative filename.
.PP
Returns true on success, or \f(CW\*(C`undef\*(C'\fR on error.
.SH "SUPPORT"
.IX Header "SUPPORT"
See the support section in the main module.
.SH "AUTHOR"
.IX Header "AUTHOR"
Adam Kennedy <adamk@cpan.org>
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2001 \- 2011 Adam Kennedy.
.PP
This program is free software; you can redistribute
it and/or modify it under the same terms as Perl itself.
.PP
The full text of the license can be found in the
\&\s-1LICENSE\s0 file included with this module.