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.\" ========================================================================
.\"
.IX Title "Class::ReturnValue 3pm"
.TH Class::ReturnValue 3pm "2022-06-26" "perl v5.34.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
Class::ReturnValue \- A return\-value object that lets you treat it 
as as a boolean, array or object
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Class::ReturnValue is a \*(L"clever\*(R" return value object that can allow
code calling your routine to expect:
    a boolean value (did it fail)
or  a list (what are the return values)
.SH "EXAMPLE"
.IX Header "EXAMPLE"
.Vb 4
\&    sub demo {
\&        my $value = shift;
\&        my $ret = Class::ReturnValue\->new();
\&        $ret\->as_array(\*(Aq0\*(Aq, \*(AqNo results found\*(Aq);
\&    
\&        unless($value) {
\&            $ret\->as_error(errno => \*(Aq1\*(Aq,
\&                               message => "You didn\*(Aqt supply a parameter.",
\&                               do_backtrace => 1);
\&        }
\&
\&        return($ret\->return_value);
\&    }
\&
\&    if (demo(\*(Aqfoo\*(Aq)){ 
\&        print "the routine succeeded with one parameter";
\&    }
\&    if (demo()) {
\&        print "The routine succeeded with 0 parameters. shouldn\*(Aqt happen";
\&    } else {
\&        print "The routine failed with 0 parameters (as it should).";
\&    }
\&
\&
\&    my $return = demo();
\&    if ($return) {
\&        print "The routine succeeded with 0 parameters. shouldn\*(Aqt happen";
\&    } else {
\&        print "The routine failed with 0 parameters (as it should). ".
\&              "Stack trace:\en".
\&        $return\->backtrace;
\&    }
\&
\&    my @return3 = demo(\*(Aqfoo\*(Aq);
\&    print "The routine got ".join(\*(Aq,\*(Aq,@return3).
\&          "when asking for demo\*(Aqs results as an array";
\&
\&
\&    my $return2 = demo(\*(Aqfoo\*(Aq);
\&
\&    unless ($return2) {
\&        print "The routine failed with a parameter. shouldn\*(Aqt happen.".
\&             "Stack trace:\en".
\&        $return2\->backtrace;
\&    }
\&
\&    my @return2_array = @{$return2}; # TODO: does this work
\&    my @return2_array2 = $return2\->as_array;
.Ve
.SH "METHODS"
.IX Header "METHODS"
.IP "new" 4
.IX Item "new"
Instantiate a new Class::ReturnValue object
.IP "as_array" 4
.IX Item "as_array"
Return the 'as_array' attribute of this object as an array.
.IP "as_array [\s-1ARRAY\s0]" 4
.IX Item "as_array [ARRAY]"
If \f(CW$self\fR is called in an array context, returns the array specified in \s-1ARRAY\s0
.IP "as_error \s-1HASH\s0" 4
.IX Item "as_error HASH"
Turns this return-value object into  an error return object.  TAkes three parameters:
.Sp
.Vb 3
\&    message
\&    do_backtrace
\&    errno 
\&
\&    \*(Aqmessage\*(Aq is a human readable error message explaining what\*(Aqs going on
\&
\&    \*(Aqdo_backtrace\*(Aq is a boolean. If it\*(Aqs true, a carp\-style backtrace will be 
\&    stored in $self\->{\*(Aqbacktrace\*(Aq}. It defaults to true
\&
\&    errno and message default to undef. errno _must_ be specified. 
\&    It\*(Aqs a numeric error number.  Any true integer value  will cause the 
\&    object to evaluate to false in a scalar context. At first, this may look a 
\&    bit counterintuitive, but it means that you can have error codes and still 
\&    allow simple use of your functions in a style like this:
\&
\&
\&        if ($obj\->do_something) {
\&            print "Yay! it worked";
\&        } else {
\&            print "Sorry. there\*(Aqs been an error.";
\&        }
\&
\&
\&        as well as more complex use like this:
\&
\&        my $retval = $obj\->do_something;
\&        
\&        if ($retval) {
\&            print "Yay. we did something\en";
\&            my ($foo, $bar, $baz) = @{$retval};
\&            my $human_readable_return = $retval;
\&        } else {
\&            if ($retval\->errno == 20) {
\&                die "Failed with error 20 (Not enough monkeys).";
\&            } else {
\&                die  $retval\->backtrace; # Die and print out a backtrace 
\&            }
\&        }
.Ve
.IP "errno" 4
.IX Item "errno"
Returns the errno if there's been an error. Otherwise, return undef
.IP "error_message" 4
.IX Item "error_message"
If there's been an error return the error message.
.IP "backtrace" 4
.IX Item "backtrace"
If there's been an error and we asked for a backtrace, return the backtrace. 
Otherwise, return undef.
.IP "error_condition" 4
.IX Item "error_condition"
If there's been an error, return undef. Otherwise return 1
.SH "AUTHOR"
.IX Header "AUTHOR"
.Vb 1
\&    Jesse Vincent <jesse@bestpractical.com>
.Ve
.SH "BUGS"
.IX Header "BUGS"
.Vb 4
\&    This module has, as yet, not been used in production code. I thing
\&    it should work, but have never benchmarked it. I have not yet used
\&    it extensively, though I do plan to in the not\-too\-distant future.
\&    If you have questions or comments,  please write me.
\&
\&    If you need to report a bug, please send mail to 
\&    <bug\-class\-returnvalue@rt.cpan.org> or report your error on the web
\&    at http://rt.cpan.org/
.Ve
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
.Vb 3
\&    Copyright (c) 2002,2003,2005,2007 Jesse Vincent <jesse@bestpractical.com>
\&    You may use, modify, fold, spindle or mutilate this module under
\&    the same terms as perl itself.
.Ve
.SH "SEE ALSO"
.IX Header "SEE ALSO"
.Vb 3
\&    Class::ReturnValue isn\*(Aqt an exception handler. If it doesn\*(Aqt
\&    do what you want, you might want look at one of the exception handlers
\&    below:
\&
\&    Error, Exception, Exceptions, Exceptions::Class
\&
\&    You might also want to look at Contextual::Return, another implementation
\&    of the same concept as this module.
.Ve