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.\" ========================================================================
.\"
.IX Title "Params::CallbackRequest::Exceptions 3pm"
.TH Params::CallbackRequest::Exceptions 3pm "2011-08-09" "perl v5.12.4" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
Params::CallbackRequest::Exceptions \- Parameter callback exception definitions
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\&  use Params::CallbackRequest::Exceptions;
\&  Params::Callback::Exception::Execution\->throw("Whoops!");
\&
\&  use Params::CallbackRequest::Exceptions abbr => [qw(throw_cb_exec)];
\&  throw_cb_exec "Whoops!";
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This module creates the exceptions used by Params::CallbackRequest and
Params::Callback. The exceptions are subclasses of Exception::Class::Base,
created by the interface defined by Exception::Class.
.SH "INTERFACE"
.IX Header "INTERFACE"
.SS "Exported Functions"
.IX Subsection "Exported Functions"
This module exports two functions by default.
.PP
\fI\f(CI\*(C`isa_cb_exception\*(C'\fI\fR
.IX Subsection "isa_cb_exception"
.PP
.Vb 10
\&  eval { something_that_dies() };
\&  if (my $err = $@) {
\&      if (isa_cb_exception($err, \*(AqAbort\*(Aq)) {
\&          print "All hands abandon ship!";
\&      } elsif (isa_cb_exception($err)) {
\&          print "I recall an exceptional fault.";
\&      } else {
\&          print "No clue.";
\&      }
\&  }
.Ve
.PP
This function takes a single argument and returns true if it's a
Params::Callback::Exception object. A second, optional argument can be used to
identify a particular subclass of Params::Callback::Exception.
.PP
\fI\f(CI\*(C`rethrow_exception\*(C'\fI\fR
.IX Subsection "rethrow_exception"
.PP
.Vb 5
\&  eval { something_that_dies() };
\&  if (my $err = $@) {
\&      # Do something intelligent, and then...
\&      rethrow_exception($err);
\&  }
.Ve
.PP
This function takes an exception as its sole argument and rethrows it. If the
argument is an object that \f(CW\*(C`can(\*(Aqthrow\*(Aq)\*(C'\fR, such as any subclass of
Exception::Class, then \f(CW\*(C`rethrow_exception()\*(C'\fR will call its rethrow method. If
not, but the argument is a reference, \f(CW\*(C`rethrow_exception()\*(C'\fR will simply die
with it. And finally, if the argument is not a reference at all,
\&\f(CW\*(C`rethrow_exception()\*(C'\fR will throw a new Params::Callback::Exception exception
with the argument used as the exception error message.
.PP
\fIAbbreviated Exception Functions\fR
.IX Subsection "Abbreviated Exception Functions"
.PP
Each of the exception classes created by Params::CallbackRequest::Exceptions has a
functional alias for its throw class method. These may be imported by passing
an array reference of the names of the abbreviated functions to import via the
\&\f(CW\*(C`abbr\*(C'\fR parameter:
.PP
.Vb 1
\&  use Params::CallbackRequest::Exceptions abbr => [qw(throw_cb_exec)];
.Ve
.PP
The names of the abbreviated functions are:
.IP "throw_cb" 4
.IX Item "throw_cb"
Params::Callback::Exception
.IP "throw_bad_key" 4
.IX Item "throw_bad_key"
Params::Callback::Exception::InvalidKey
.IP "throw_cb_exec" 4
.IX Item "throw_cb_exec"
Params::Callback::Exception::Execution
.IP "throw_bad_params" 4
.IX Item "throw_bad_params"
Params::Callback::Exception::Params
.IP "throw_abort" 4
.IX Item "throw_abort"
Params::Callback::Exception::Abort
.SS "Exception Classes"
.IX Subsection "Exception Classes"
The exception classes created by Params::Callback::Exception are as follows:
.PP
\fIParams::Callback::Exception\fR
.IX Subsection "Params::Callback::Exception"
.PP
This is the base class for all Params::Callback exception classes. Its
functional alias is \f(CW\*(C`throw_cb\*(C'\fR.
.PP
\fIParams::Callback::Exception::InvalidKey\fR
.IX Subsection "Params::Callback::Exception::InvalidKey"
.PP
Params::CallbackRequest throws this exception when a callback key in the parameter
hash passed to \f(CW\*(C`new()\*(C'\fR has no corresponding callback. In addition to the
attributes offered by Exception::Class::Base, this class also features the
attribute \f(CW\*(C`callback_key\*(C'\fR. Use the \f(CW\*(C`callback_key()\*(C'\fR accessor to see what
callback key triggered the
exception. Params::Callback::Exception::InvalidKey's functional alias is
\&\f(CW\*(C`throw_bad_key\*(C'\fR.
.PP
\fIParams::Callback::Exception::Execution\fR
.IX Subsection "Params::Callback::Exception::Execution"
.PP
This is the exception thrown by Params::CallbackRequest's default exception
handler when a callback subroutine or method dies. In addition to the
attributes offered by Exception::Class::Base, this class also features the
attributes \f(CW\*(C`callback_key\*(C'\fR, which corresponds to the parameter key that
triggered the callback, and \f(CW\*(C`callback_error\*(C'\fR which is the error thrown by the
callback subroutine or method. Params::Callback::Exception::Execution's
functional alias is \f(CW\*(C`throw_cb_exec\*(C'\fR.
.PP
\fIParams::Callback::Exception::Params\fR
.IX Subsection "Params::Callback::Exception::Params"
.PP
This is the exception thrown when an invalid parameter is passed to
Params::CallbackRequest's or Params::Callback's \f(CW\*(C`new()\*(C'\fR constructors. Its
functional alias is \f(CW\*(C`throw_bad_params\*(C'\fR.
.PP
\fIParams::Callback::Exception::Abort\fR
.IX Subsection "Params::Callback::Exception::Abort"
.PP
This is the exception thrown by Params::Callback's \f(CW\*(C`abort()\*(C'\fR method.
functional alias is \f(CW\*(C`throw_cb\*(C'\fR. In addition to the attributes offered by
Exception::Class::Base, this class also features the attribute
\&\f(CW\*(C`aborted_value\*(C'\fR attribute. Use the \f(CW\*(C`aborted_value()\*(C'\fR accessor to see what
value was passed to \f(CW\*(C`abort()\*(C'\fR. Params::Callback::Exception::Abort's
functional alias is \f(CW\*(C`throw_abort\*(C'\fR.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Params::Callback is the base class for all callback
classes.
.PP
Params::CallbackRequest sets up callbacks for execution.
.PP
Exception::Class defines the interface for the exception
classes created here.
.SH "SUPPORT"
.IX Header "SUPPORT"
This module is stored in an open GitHub
repository <http://github.com/theory/params-callbackrequest/>. Feel free to
fork and contribute!
.PP
Please file bug reports via GitHub
Issues <http://github.com/theory/params-callbackrequest/issues/> or by sending
mail to
bug\-params\-callbackrequest@rt.cpan.org <mailto:bug-params-callbackrequest@rt.cpan.org>.
.SH "AUTHOR"
.IX Header "AUTHOR"
David E. Wheeler <david@justatheory.com>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
Copyright 2003\-2011 David E. Wheeler. Some Rights Reserved.
.PP
This library is free software; you can redistribute it and/or modify it under
the same terms as Perl itself.