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<title>Message::Util::Error - manakai's Common Error Handling Module</title> |
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<body> |
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|
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<p><a name="__index__"></a></p> |
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<!-- INDEX BEGIN --> |
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|
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<ul> |
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|
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<li><a href="#name">NAME</a></li> |
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<li><a href="#synopsis">SYNOPSIS</a></li> |
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<li><a href="#description">DESCRIPTION</a></li> |
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<li><a href="#accessing_error_information">ACCESSING ERROR INFORMATION</a></li> |
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<ul> |
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|
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<li><a href="#loading_try_and_catch_support">Loading <code>try</code> and <code>catch</code> Support</a></li> |
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<li><a href="#methods_on_error_objects">Methods on Error Objects</a></li> |
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</ul> |
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|
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<li><a href="#throwing_errors">THROWING ERRORS</a></li> |
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<ul> |
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|
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<li><a href="#error_classes">Error Classes</a></li> |
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<li><a href="#error_type_definitions">Error Type Definitions</a></li> |
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<li><a href="#throwing_an_error">Throwing an Error</a></li> |
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<li><a href="#___report_error_method"><code>___report_error</code> Method</a></li> |
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<li><a href="#error_message_construction">Error Message Construction</a></li> |
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<li><a href="#formatter_message__util__error__formatter">Formatter Message::Util::Error::formatter</a></li> |
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</ul> |
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|
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<li><a href="#example">EXAMPLE</a></li> |
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<li><a href="#see_also">SEE ALSO</a></li> |
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<li><a href="#author">AUTHOR</a></li> |
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<li><a href="#license">LICENSE</a></li> |
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</ul> |
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<!-- INDEX END --> |
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|
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<hr /> |
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<p> |
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</p> |
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<h1><a name="name">NAME</a></h1> |
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<p>Message::Util::Error - manakai's Common Error Handling Module</p> |
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<p> |
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</p> |
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<hr /> |
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<h1><a name="synopsis">SYNOPSIS</a></h1> |
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<p>If you want to catch an exception, whose class |
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is <em>YourExceptionClass</em>, throwed by a class <em>YourClass</em>:</p> |
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<pre> |
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use YourClass; |
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use Message::Util::Error; |
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|
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my $obj = YourClass->new; |
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|
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try { |
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$obj->method_that_throw_an_eception; |
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} catch YourExceptionClass with { |
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my $err = shift; |
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if ($err->type eq 'NOT_SUPPORTED_ERR') { |
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$err->throw; # die unless catched by upper-level |try| clause (if any) |
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} else { |
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warn $err; |
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} |
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};</pre> |
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<p>If you want to build a class <em>YourClass</em> that |
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throws an exception based on <code>Message::Util::Error</code>:</p> |
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<pre> |
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package YourClass; |
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|
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sub method_that_throw_an_exception ($) { |
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my $self = shift; |
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report YourExceptionClass |
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-object => $self, |
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-type => 'EXAMPLE_ERR', |
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-subtype => 'EXAMPLE_SPECIFIC_ERR'; |
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} # method_that_throw_an_exception |
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|
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## |report| calls back this method. If this method |throw|s |
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## the exception, then it is really thrown. |
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sub ___report_error ($$) { |
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my ($self, $err) = @_; |
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if ($err->type_def->{level} eq 'warning') { |
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warn $err; |
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} else { |
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$err->throw; |
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} |
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} # ___report_error |
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|
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package YourExceptionClass; |
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use Message::Util::Error; |
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push our @ISA, 'Message::Util::Error'; |
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|
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sub ___error_def () { |
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return { |
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EXAMPLE_ERR => { |
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-description => q<An example error condition>, |
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-subtype => { |
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EXAMPLE_SPECIFIC_ERR => { |
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-description => q<A specific example error condition>, |
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}, |
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}, |
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level => 'fatal', |
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}, |
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}; |
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} # ___error_def</pre> |
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<p> |
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</p> |
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<hr /> |
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<h1><a name="description">DESCRIPTION</a></h1> |
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<p>Various manakai classes throws exceptions, in particular |
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<code>DOMException</code>s in DOM implementation classes. In addition, |
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it might report other kinds of errors, such as <code>DOMError</code> |
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as defined in DOM Level 3 Core specification. This module, |
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<code>Message::Util::Error</code>, provides an integrated framework |
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for reporting exceptions, errors, warnings, and so on.</p> |
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<p>The <code>Message::Util::Error</code> exception framework is built on |
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the top of the Perl module <code>Error</code>, which apply to Perl scripts |
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the <code>try</code> and <code>catch</code> functionalities. Exceptions |
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thrown using <code>Message::Util::Error</code> exception framework |
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are also able to be catched by the <code>catch</code> clause as in |
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the original <code>Error</code> module. For more information on |
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usage for <code>try</code>, <code>catch</code>, and other clauses, see |
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the documentatin for the <code>Error</code> module. This document |
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describes some <code>Message::Util::Error</code>-specific conventions, |
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mainly targeted for manakai module authors.</p> |
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<p>For other usages of the framework, such as <code>DOMError</code>, |
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see documentation for each module.</p> |
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<p>This module is part of manakai.</p> |
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<p> |
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</p> |
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<hr /> |
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<h1><a name="accessing_error_information">ACCESSING ERROR INFORMATION</a></h1> |
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<p> |
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</p> |
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<h2><a name="loading_try_and_catch_support">Loading <code>try</code> and <code>catch</code> Support</a></h2> |
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<p>If you'd like to use <code>try</code> and <code>catch</code> clauses, you |
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have to import these names by:</p> |
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<pre> |
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use Message::Util::Error;</pre> |
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<p>Note that the example above is equivalent to:</p> |
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<pre> |
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use Error qw(:try);</pre> |
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<p>except that in the former example <code>Message::Util::Error</code> |
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module is also loaded if not yet.</p> |
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<p> |
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</p> |
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<h2><a name="methods_on_error_objects">Methods on Error Objects</a></h2> |
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<p><em>Any method defined on an <code>Error</code> object is also available</em> |
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for <code>Message::Util::Error</code> objects with the same semantics |
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(though some might be overridden). In addition, |
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a few methods are added for <code>Message::Util::Error</code> objects.</p> |
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<dl> |
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<dt><strong><a name="item_code"><em>$code</em> = <em>$err</em>->code;</a></strong><br /> |
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</dt> |
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<dd> |
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Returns the code of the error. |
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</dd> |
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<dd> |
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<p>If the definition for the error type has a code associated, |
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then it is returned. Otherwise, <code>0</code> is returned.</p> |
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</dd> |
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<dd> |
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<p>This method is added for DOM compatibility.</p> |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_subtype"><em>$subtype</em> = <em>$err</em>->subtype;</a></strong><br /> |
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</dt> |
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<dd> |
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Returns the subtype of the error, if specified when the |
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error object is created, or <code>undef</code> otherwise. |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_text"><em>$text</em> = <em>$err</em>->text;</a></strong><br /> |
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</dt> |
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<dd> |
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Returns the text of the error. |
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</dd> |
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<dd> |
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<p><em>This method is defined in <code>Error</code> module but overridden.</em> |
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If the definition for the error subtype, if any, has a description, |
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then it is returned. Otherwise, if the definition for the error type |
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has a description, then it is returned. Otherwise, |
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same as <code>Error</code>'s definition, i.e. the text specified |
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when the <code>Error</code> object is created, if any, or <code>undef</code> otherwise, |
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is returned.</p> |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_type"><em>$text</em> = <em>$err</em>->type;</a></strong><br /> |
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</dt> |
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<dd> |
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Returns the type of the error specified when the error is created. |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_type_def"><em>$def</em> = <em>$err</em>->type_def;</a></strong><br /> |
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</dt> |
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<dd> |
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Returns the definition for the error type, if any, |
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or the definition for the <code>UNKNOWN</code> type, otherwise. |
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For the content of the error type definition, |
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see <a href="#error_type_definitions">Error Type Definitions</a>. Applications |
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MUST NOT modify the error type definition. If modified |
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then the result is undefined and it might make the error handling |
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behaviour inconsistent or incorrect. |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_value"><em>$value</em> = <em>$err</em>->value; <em>$value</em> = 0+<em>$err</em>;</a></strong><br /> |
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</dt> |
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<dd> |
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Returns the value that can be associated with the error. |
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</dd> |
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<dd> |
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<p><em>This method is defined in <code>Error</code> module but overridden.</em> |
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If the definition for the error type has a code associated, |
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then it is returned. Otherwise, |
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same as <code>Error</code>'s definition, i.e. the value specified |
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when the <code>Error</code> object is created, if any, or <code>undef</code> otherwise, |
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is returned.</p> |
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</dd> |
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<p></p></dl> |
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<p> |
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</p> |
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<hr /> |
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<h1><a name="throwing_errors">THROWING ERRORS</a></h1> |
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<p>@@</p> |
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<p>1. Define an error class.</p> |
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<p>2. Define the <code>___report_error</code> method to the class |
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whose methods will report errors. (REQUIRED |
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if you use <code>report</code>.)</p> |
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<p>3. Define an error message template class. (REQUIRED |
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if you want to extend the error message parameter set.)</p> |
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<p>4. Put <code>report</code> or <code>throw</code> where you want to report |
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or throw an error.</p> |
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<p>5. Ensure the error class is loaded when any statement |
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added by Step 4 is executed.</p> |
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<p> |
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</p> |
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<h2><a name="error_classes">Error Classes</a></h2> |
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<p>@@</p> |
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<p> |
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</p> |
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<h2><a name="error_type_definitions">Error Type Definitions</a></h2> |
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<p>@@</p> |
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<p>Error type:</p> |
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<dl> |
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<dt><strong><a name="item__2dcode">-code</a></strong><br /> |
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</dt> |
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<dd> |
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Numeric error code for the type. If specified, |
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it MUST be a number. |
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</dd> |
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<p></p> |
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<dt><strong><a name="item__2ddescription">-description</a></strong><br /> |
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</dt> |
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<dd> |
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A template that is used to create the description |
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for an error with that type. |
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@@ See @@ for template syntax. |
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</dd> |
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<p></p> |
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<dt><strong><a name="item__2dsubtype">-subtype</a></strong><br /> |
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</dt> |
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<dd> |
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A reference to hash that contains pairs of |
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error subtype nams and error subtype definitions. |
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It MAY contain zero or more error subtypes. |
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</dd> |
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<p></p></dl> |
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<p>Error subtype:</p> |
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<dl> |
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<dt><strong>-description</strong><br /> |
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</dt> |
| 278 |
<dd> |
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A template that is used to create the description |
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for an error with that subtype. |
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@@ See @@ for template syntax. |
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</dd> |
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<p></p></dl> |
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<p>Any other value starts with <code>-</code> is reserved for future extension |
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and MUST NOT be used for any purpose until it is eventually defined. |
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Values <em>not</em> start with <code>-</code> MAY be used for subclass-specific |
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error type/subtype properties.</p> |
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<p> |
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</p> |
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<h2><a name="throwing_an_error">Throwing an Error</a></h2> |
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<p>@@</p> |
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<dl> |
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<dt><strong><a name="item_def">-def (MUST NOT be specified)</a></strong><br /> |
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</dt> |
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<dd> |
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The definition for the error type. |
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</dd> |
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<dd> |
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<p>This parameter MUST NOT be specified when a |
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<code>Message::Util::Error</code> object is created. |
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It will be supplied by the constructor of the error object. |
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If any value is specified, it will be ignored.</p> |
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</dd> |
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<dd> |
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<p>If no definition for the error type is found, |
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then the definition for the <code>UNKNOWN</code> type is used; |
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if there is no such definition, then the error constructor |
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<code>die</code>s.</p> |
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</dd> |
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<p></p> |
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<dt><strong><a name="item_file">-file (MUST NOT be specified)</a></strong><br /> |
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</dt> |
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<dd> |
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The file name where an error is reported. |
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</dd> |
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<dd> |
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<p>This parameter MUST NOT be specified when a |
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<code>Message::Util::Error</code> object is created. |
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It will be supplied by the constructor of the error object. |
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If any value is specified, it will be ignored.</p> |
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</dd> |
| 322 |
<p></p> |
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<dt><strong><a name="item_line">-line (MUST NOT be specified)</a></strong><br /> |
| 324 |
</dt> |
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<dd> |
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The line number where an error is reported. |
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</dd> |
| 328 |
<dd> |
| 329 |
<p>This parameter MUST NOT be specified when a |
| 330 |
<code>Message::Util::Error</code> object is created. |
| 331 |
It will be supplied by the constructor of the error object. |
| 332 |
If any value is specified, it will be ignored.</p> |
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</dd> |
| 334 |
<p></p> |
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<dt><strong><a name="item__2dobject">-object</a></strong><br /> |
| 336 |
</dt> |
| 337 |
<dd> |
| 338 |
The object for which an error is reported. |
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</dd> |
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<dd> |
| 341 |
<p>If specified, the value MUST be an object |
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that has a <code>___report_error</code> method. |
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Otherwise, Perl will report some error.</p> |
| 344 |
</dd> |
| 345 |
<p></p> |
| 346 |
<dt><strong><a name="item_package">-package (MUST NOT be specified)</a></strong><br /> |
| 347 |
</dt> |
| 348 |
<dd> |
| 349 |
The package name where an error is reported. |
| 350 |
</dd> |
| 351 |
<dd> |
| 352 |
<p>This parameter MUST NOT be specified when a |
| 353 |
<code>Message::Util::Error</code> object is created. |
| 354 |
It will be supplied by the constructor of the error object. |
| 355 |
If any value is specified, it will be ignored.</p> |
| 356 |
</dd> |
| 357 |
<p></p> |
| 358 |
<dt><strong><a name="item_stacktrace">-stacktrace (MUST NOT be specified)</a></strong><br /> |
| 359 |
</dt> |
| 360 |
<dd> |
| 361 |
The trace of the function call stack (used by <code>Error</code> module). |
| 362 |
</dd> |
| 363 |
<dd> |
| 364 |
<p>This parameter MUST NOT be specified when a |
| 365 |
<code>Message::Util::Error</code> object is created. |
| 366 |
It will be supplied by the constructor of the error object. |
| 367 |
If any value is specified, it will be ignored.</p> |
| 368 |
</dd> |
| 369 |
<p></p> |
| 370 |
<dt><strong><a name="item_stacktrace_">-stacktrace_ (MUST NOT be specified)</a></strong><br /> |
| 371 |
</dt> |
| 372 |
<dd> |
| 373 |
The trace of the function call stack (used by <code>Message::Util::Error</code> |
| 374 |
module). |
| 375 |
</dd> |
| 376 |
<dd> |
| 377 |
<p>This parameter MUST NOT be specified when a |
| 378 |
<code>Message::Util::Error</code> object is created. |
| 379 |
It will be supplied by the constructor of the error object. |
| 380 |
If any value is specified, it will be ignored.</p> |
| 381 |
</dd> |
| 382 |
<p></p> |
| 383 |
<dt><strong>-subtype</strong><br /> |
| 384 |
</dt> |
| 385 |
<dd> |
| 386 |
The subtype of the error. It may or may not be specified. |
| 387 |
</dd> |
| 388 |
<p></p> |
| 389 |
<dt><strong><a name="item__2dtext">-text</a></strong><br /> |
| 390 |
</dt> |
| 391 |
<dd> |
| 392 |
The text of the error. Note that this option is less |
| 393 |
useful in <code>Message::Util::Error</code> where <a href="#item__2ddescription"><code>-description</code></a> |
| 394 |
in error type/subtype definitions take precedence in the <a href="#item_text"><code>text</code></a> method. |
| 395 |
</dd> |
| 396 |
<p></p> |
| 397 |
<dt><strong>-type (REQUIRED)</strong><br /> |
| 398 |
</dt> |
| 399 |
<dd> |
| 400 |
The error type. |
| 401 |
</dd> |
| 402 |
<dd> |
| 403 |
<p>This parameter MUST be specified when |
| 404 |
a <code>Message::Util::Error</code> object is created. |
| 405 |
If this option is missing when creating an error object, |
| 406 |
then the error constructor <code>die</code>s.</p> |
| 407 |
</dd> |
| 408 |
<p></p> |
| 409 |
<dt><strong><a name="item__2dvalue">-value</a></strong><br /> |
| 410 |
</dt> |
| 411 |
<dd> |
| 412 |
The value of the error. Note that this option is less |
| 413 |
useful in <code>Message::Util::Error</code> where <a href="#item__2dcode"><code>-code</code></a> |
| 414 |
in error type definition take precedence in the <a href="#item_value"><code>value</code></a> method. |
| 415 |
</dd> |
| 416 |
<p></p></dl> |
| 417 |
<p>Any other value starts with <code>-</code> is reserved for future extension |
| 418 |
and MUST NOT be used for any purpose until it is eventually defined. |
| 419 |
Values <em>not</em> start with <code>-</code> MAY be used for subclass-specific |
| 420 |
error properties.</p> |
| 421 |
<p> |
| 422 |
</p> |
| 423 |
<h2><a name="___report_error_method"><code>___report_error</code> Method</a></h2> |
| 424 |
<p>@@</p> |
| 425 |
<p> |
| 426 |
</p> |
| 427 |
<h2><a name="error_message_construction">Error Message Construction</a></h2> |
| 428 |
<p>@@ NEED TO BE REWRITTEN</p> |
| 429 |
<p>Human readable error message text, returned by <a href="#item_text"><code>text</code></a> method, |
| 430 |
is generated from <code>description</code> parameter of error definition.</p> |
| 431 |
<p>Format defined by <a href="../../Message/Util/Formatter.html">the Message::Util::Formatter manpage</a> is used to specify |
| 432 |
<code>description</code> parameter and it is processed by the formatter.</p> |
| 433 |
<dl> |
| 434 |
<dt><strong><a name="item_sub_error_subclass_3a_3a_formatter_package___7b_re">sub ERROR_SUBCLASS::_FORMATTER_PACKAGE_ { return $class_name }</a></strong><br /> |
| 435 |
</dt> |
| 436 |
<dd> |
| 437 |
Subclass can define <code>_FORMATTER_PACKAGE_</code> method |
| 438 |
to define class name of the formatter. Defaulted to |
| 439 |
<code>Message::Util::Error::formatter</code>. |
| 440 |
</dd> |
| 441 |
<dd> |
| 442 |
<p>Unless you wish to use additional rules in template text |
| 443 |
(<code>description</code> parameter), you don't need to define this |
| 444 |
method in your subclass.</p> |
| 445 |
</dd> |
| 446 |
<dd> |
| 447 |
<p>Class returned by this method MUST be a subclass (descender class) of |
| 448 |
<code>Message::Util::Formatter::Base</code>.</p> |
| 449 |
</dd> |
| 450 |
<p></p></dl> |
| 451 |
<p> |
| 452 |
</p> |
| 453 |
<h2><a name="formatter_message__util__error__formatter">Formatter Message::Util::Error::formatter</a></h2> |
| 454 |
<p>In addition to rules defined in <code>Message::Util::Formatter::Text</code>, |
| 455 |
formatter <code>Message::Util::Error::formatter</code> defines some rules:</p> |
| 456 |
<dl> |
| 457 |
<dt><strong><a name="item__name_">%name;</a></strong><br /> |
| 458 |
</dt> |
| 459 |
<dd> |
| 460 |
Error type name (<code>-type</code> parameter specified when error is thrown) |
| 461 |
</dd> |
| 462 |
<p></p> |
| 463 |
<dt><strong><a name="item_t">%t (name => parameter-name);</a></strong><br /> |
| 464 |
</dt> |
| 465 |
<dd> |
| 466 |
Parameter value specified when error is thrown |
| 467 |
</dd> |
| 468 |
<p></p></dl> |
| 469 |
<p> |
| 470 |
</p> |
| 471 |
<hr /> |
| 472 |
<h1><a name="example">EXAMPLE</a></h1> |
| 473 |
<p>@@ MAYBE WE CAN REMOVE THIS SECTION</p> |
| 474 |
<p>To make a new error class:</p> |
| 475 |
<pre> |
| 476 |
package SomeExceptionClass; |
| 477 |
use Message::Util::Error; |
| 478 |
push our @ISA, 'Message::Util::Error'; |
| 479 |
|
| 480 |
## [REQUIRED] Error types |
| 481 |
sub ___error_def { |
| 482 |
## Returns a reference to hash defining error type |
| 483 |
return { |
| 484 |
ERROR_NAME => { |
| 485 |
description => q(%name;: %t (name => what); is bad), |
| 486 |
level => 'fatal', |
| 487 |
... |
| 488 |
}, |
| 489 |
WARNING_NAME => { |
| 490 |
description => q(%name;: %t (name => what); might be bad), |
| 491 |
level => 'warn', |
| 492 |
... |
| 493 |
}, |
| 494 |
... |
| 495 |
}; |
| 496 |
} |
| 497 |
|
| 498 |
## [OPTIONAL] Package name of formatter constructing error message |
| 499 |
## (Default: Message::Util::Error::formatter) |
| 500 |
sub _FORMATTER_PACKAGE_ () { 'SomeFormatterClass' }</pre> |
| 501 |
<p>Throwing exception:</p> |
| 502 |
<pre> |
| 503 |
use SomeExceptionClass; |
| 504 |
... |
| 505 |
do something; |
| 506 |
... |
| 507 |
throw SomeExceptionClass -type => 'ERROR_NAME', |
| 508 |
what => 'Example';</pre> |
| 509 |
<p>If you implements an object-oriented class:</p> |
| 510 |
<pre> |
| 511 |
package SomeModule; |
| 512 |
use SomeExceptionClass; |
| 513 |
|
| 514 |
sub some_method { |
| 515 |
my $self = shift; |
| 516 |
... |
| 517 |
report SomeExceptionClass |
| 518 |
-type => 'ERROR_NAME', |
| 519 |
what => 'Non-oo programing', |
| 520 |
-object => $self, method => 'some_method' |
| 521 |
unless $oo; |
| 522 |
... |
| 523 |
report SomeExceptionClass |
| 524 |
-type => 'WARNING_NAME', |
| 525 |
what => 'This module', |
| 526 |
-object => $self, method => 'some_method'; |
| 527 |
... |
| 528 |
} |
| 529 |
|
| 530 |
## If you use "report", you must implements this internal method |
| 531 |
sub ___report_error ($$;%) { |
| 532 |
my ($self, $err, %option) = @_; |
| 533 |
## Throwing if fatal |
| 534 |
if ($err->{def}->{level} eq 'fatal') { |
| 535 |
$err->throw; |
| 536 |
print "This text never printed"; |
| 537 |
## Otherwise warning only |
| 538 |
} else { |
| 539 |
warn $err->stringify; |
| 540 |
print "This text IS printed"; |
| 541 |
} |
| 542 |
}</pre> |
| 543 |
<p> |
| 544 |
</p> |
| 545 |
<hr /> |
| 546 |
<h1><a name="see_also">SEE ALSO</a></h1> |
| 547 |
<p><em>Error</em></p> |
| 548 |
<p><a href="../../Message/DOM/DOMException.html">the Message::DOM::DOMException manpage</a></p> |
| 549 |
<p><a href="../../Message/DOM/DOMError.html">the Message::DOM::DOMError manpage</a></p> |
| 550 |
<p> |
| 551 |
</p> |
| 552 |
<hr /> |
| 553 |
<h1><a name="author">AUTHOR</a></h1> |
| 554 |
<p>Wakaba <<a href="mailto:w@suika.fam.cx">w@suika.fam.cx</a>></p> |
| 555 |
<p> |
| 556 |
</p> |
| 557 |
<hr /> |
| 558 |
<h1><a name="license">LICENSE</a></h1> |
| 559 |
<p>Copyright 2003-2007 Wakaba <<a href="mailto:w@suika.fam.cx">w@suika.fam.cx</a>></p> |
| 560 |
<p>This program is free software; you can redistribute it and/or |
| 561 |
modify it under the same terms as Perl itself.</p> |
| 562 |
|
| 563 |
</body> |
| 564 |
|
| 565 |
</html> |
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