1Graph::Error(3)       User Contributed Perl Documentation      Graph::Error(3)
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NAME

6       GD::Graph::Error - Error handling for GD::Graph classes
7

SYNOPSIS

9       use GD::Graph::Error_subclass;
10

DESCRIPTION

12       This class is a parent for all GD::Graph classes, including
13       GD::Graph::Data, and offers error and warning handling and some
14       debugging control.
15
16       Errors are stored in a lexical hash in this package, so the
17       implementation of the subclass should be irrelevant.
18

PUBLIC METHODS

20       These methods can be used by users of any of the subclasses of
21       GD::Graph::Error to get at the errors of objects or classes.
22
23   $object->error() OR Class->error()
24       Returns a list of all the errors that the current object has
25       accumulated. In scalar context, returns the last error. If called as a
26       class method it works at a class level. This is handy when a
27       constructor fails, for example:
28
29         my $data = GD::Graph::Data->new()
30             or die GD::Graph::Data->error;
31         $data->read(file => '/foo/bar.data')
32             or die $data->error;
33
34       or if you really are only interested in the last error:
35
36         $data->read(file => '/foo/bar.data')
37             or die scalar $data->error;
38
39       This implementation does not clear the error list, so if you don't die
40       on errors, you will need to make sure to never ask for anything but the
41       last error (put this in scalar context) or to call "clear_error()" now
42       and again.
43
44       Errors are more verbose about where the errors originated if the
45       $GD::Graph::Error::Debug variable is set to a true value, and even more
46       verbose if this value is larger than 5.
47
48       If $Debug is larger than 3, both of these will always return the full
49       list of errors and warnings (although the meaning of "has_warning" and
50       "has_error" does not change).
51
52   $object->has_error() OR Class->has_error()
53   $object->has_warning() OR Class->has_warning()
54       Returns true if there are pending errors (warnings) for the object (or
55       class). To be more precise, it returns a list of errors in list
56       context, and the number of errors in scalar context.
57
58       This allows you to check for errors and warnings after a large number
59       of operations which each might fail:
60
61         $data->read(file => '/foo/bar.data') or die $data->error;
62         while (my @foo = $sth->fetchrow_array)
63         {
64             $data->add_point(@foo);
65         }
66         $data->set_x(12, 'Foo');
67         $data->has_warning and warn $data->warning;
68         $data->has_error   and die  $data->error;
69
70       The reason to call this, instead of just calling "error()" or
71       "warning()" and looking at its return value, is that this method is
72       much more efficient and fast.
73
74       If you want to count anything as bad, just set $ErrorLevel to 0, after
75       which you only need to call "has_error".
76
77   $object->clear_errors() or Class->clear_errors()
78       Clears all outstanding errors.
79

PROTECTED METHODS

81       These methods are only to be called from within this class and its
82       Subclasses.
83
84   $object->_set_error(arg) or Class->_set_error(arg)
85   $object->_set_warning(arg) or Class->_set_warning(arg)
86       Subclasses call this to set an error. The argument can be a reference
87       to an array, of which the first element should be the error level, and
88       the second element the error message. Alternatively, it can just be the
89       message, in which case the error level will be assumed to be
90       $ErrorLevel.
91
92       If the error level is >= $CriticalLevel the program will die, using
93       Carp::croak to display the current message, as well as all the other
94       error messages pending.
95
96       In the current implementation these are almost identical when called
97       with a scalar argument, except that the default error level is
98       different. When called with an array reference, they are identical in
99       function. This may change in the future. They're mainly here for code
100       clarity.
101
102   $object->_move_errors
103       Move errors from an object into the class it belongs to.  This can be
104       useful if something nasty happens in the constructor, while
105       instantiating one of these objects, and you need to move these errors
106       into the class space before returning. (see GD::Graph::Data::new for an
107       example)
108

VARIABLES

110   $GD::Graph::Error::Debug
111       The higher this value, the more verbose error messages will be. At the
112       moment, any true value will cause the line number and source file of
113       the caller at the top of the stack to be included, a value of more than
114       2 will include the error severity, and a value of more than 5 will also
115       include the direct caller's (i.e. the spot where the error message was
116       generated) line number and package. Default: 0.
117
118   $GD::Graph::Error::ErrorLevel
119       Errors levels below this value will be counted as warnings, and error
120       levels above (and inclusive) up to $CriticalLevel will be counted as
121       errors. This is also the default error level for the "_set_error()"
122       method. This value should be 0 or larger, and smaller than
123       $CriticalLevel. Default: 5.
124
125   $GD::Graph::Error::CriticalLevel
126       Any errorlevel of or above this level will immediately cause the
127       program to die with the specified message, using Carp::croak. Default:
128       10.
129

NOTES

131       As with all Modules for Perl: Please stick to using the interface. If
132       you try to fiddle too much with knowledge of the internals of this
133       module, you could get burned. I may change them at any time.
134

AUTHOR

136       Martien Verbruggen <mgjv@tradingpost.com.au>
137
138   Copyright
139       (c) Martien Verbruggen.
140
141       All rights reserved. This package is free software; you can
142       redistribute it and/or modify it under the same terms as Perl itself.
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SEE ALSO

145       GD::Graph, GD::Graph::Data
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149perl v5.34.0                      2021-07-22                   Graph::Error(3)
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