GD::Graph::Error - phpMan

NAME
    GD::Graph::Error - Error handling for GD::Graph classes

SYNOPSIS
    use GD::Graph::Error_subclass;

DESCRIPTION
    This class is a parent for all GD::Graph classes, including
    GD::Graph::Data, and offers error and warning handling and some
    debugging control.

    Errors are stored in a lexical hash in this package, so the
    implementation of the subclass should be irrelevant.

PUBLIC METHODS
    These methods can be used by users of any of the subclasses of
    GD::Graph::Error to get at the errors of objects or classes.

  $object->error() OR Class->error()
    Returns a list of all the errors that the current object has
    accumulated. In scalar context, returns the last error. If called as a
    class method it works at a class level. This is handy when a constructor
    fails, for example:

      my $data = GD::Graph::Data->new()
          or die GD::Graph::Data->error;
      $data->read(file => '/foo/bar.data')
          or die $data->error;

    or if you really are only interested in the last error:

      $data->read(file => '/foo/bar.data')
          or die scalar $data->error;

    This implementation does not clear the error list, so if you don't die
    on errors, you will need to make sure to never ask for anything but the
    last error (put this in scalar context) or to call "clear_error()" now
    and again.

    Errors are more verbose about where the errors originated if the
    $GD::Graph::Error::Debug variable is set to a true value, and even more
    verbose if this value is larger than 5.

    If $Debug is larger than 3, both of these will always return the full
    list of errors and warnings (although the meaning of "has_warning" and
    "has_error" does not change).

  $object->has_error() OR Class->has_error()
  $object->has_warning() OR Class->has_warning()
    Returns true if there are pending errors (warnings) for the object (or
    class). To be more precise, it returns a list of errors in list context,
    and the number of errors in scalar context.

    This allows you to check for errors and warnings after a large number of
    operations which each might fail:

      $data->read(file => '/foo/bar.data') or die $data->error;
      while (my @foo = $sth->fetchrow_array)
      {
          $data->add_point(@foo);
      }
      $data->set_x(12, 'Foo');
      $data->has_warning and warn $data->warning;
      $data->has_error   and die  $data->error;

    The reason to call this, instead of just calling "error()" or
    "warning()" and looking at its return value, is that this method is much
    more efficient and fast.

    If you want to count anything as bad, just set $ErrorLevel to 0, after
    which you only need to call "has_error".

  $object->clear_errors() or Class->clear_errors()
    Clears all outstanding errors.

PROTECTED METHODS
    These methods are only to be called from within this class and its
    Subclasses.

  $object->_set_error(*arg*) or Class->_set_error(*arg*)
  $object->_set_warning(*arg*) or Class->_set_warning(*arg*)
    Subclasses call this to set an error. The argument can be a reference to
    an array, of which the first element should be the error level, and the
    second element the error message. Alternatively, it can just be the
    message, in which case the error level will be assumed to be
    $ErrorLevel.

    If the error level is >= $CriticalLevel the program will die, using
    Carp::croak to display the current message, as well as all the other
    error messages pending.

    In the current implementation these are almost identical when called
    with a scalar argument, except that the default error level is
    different. When called with an array reference, they are identical in
    function. This may change in the future. They're mainly here for code
    clarity.

  $object->_move_errors
    Move errors from an object into the class it belongs to. This can be
    useful if something nasty happens in the constructor, while
    instantiating one of these objects, and you need to move these errors
    into the class space before returning. (see GD::Graph::Data::new for an
    example)

VARIABLES
  $GD::Graph::Error::Debug
    The higher this value, the more verbose error messages will be. At the
    moment, any true value will cause the line number and source file of the
    caller at the top of the stack to be included, a value of more than 2
    will include the error severity, and a value of more than 5 will also
    include the direct caller's (i.e. the spot where the error message was
    generated) line number and package. Default: 0.

  $GD::Graph::Error::ErrorLevel
    Errors levels below this value will be counted as warnings, and error
    levels above (and inclusive) up to $CriticalLevel will be counted as
    errors. This is also the default error level for the "_set_error()"
    method. This value should be 0 or larger, and smaller than
    $CriticalLevel. Default: 5.

  $GD::Graph::Error::CriticalLevel
    Any errorlevel of or above this level will immediately cause the program
    to die with the specified message, using Carp::croak. Default: 10.

NOTES
    As with all Modules for Perl: Please stick to using the interface. If
    you try to fiddle too much with knowledge of the internals of this
    module, you could get burned. I may change them at any time.

AUTHOR
    Martien Verbruggen <mgjv AT tradingpost.au>

  Copyright
    (c) Martien Verbruggen.

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

SEE ALSO
    GD::Graph, GD::Graph::Data