Fellow Monks,

Please shine your blessed light on this:

I was writing some code using Image::Magick and found myself repeating lines like:

   $err = $image->DoSomething;
   if("$err") {  # one must evaluate the return value
                 # in string context, according to the 
                 # PerlMagick docs
      die ("Can't do Something: $err\n");
   }
[download]

Which I find less than esthetical for several reasons. And even now I::M sometimes printed a warning in stead of giving an error message.

I'd rather do:

    eval {
       $image->DoSomething;
       $image->DoSomethingElse;
       $image->Save;
    };
    if($@) { handle_the_error; }
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So I started Image::Magick::Exceptions, borrowing from Simon Cozens' Class::Wrap:

package Image::Magick::Exceptions;
use warnings;
use strict;

use Exception::Class qw/Image::Magick::Exception/;

{   no strict;
    no warnings qw/redefine prototype/;

    my $class = "Image::Magick";

    for my $method (keys %{$class."::"})
    {
        my $cmethod = "${class}::$method";

        if (   defined *{$cmethod}{CODE}
           and $method ne 'new'    
           and $method !~ /^[A-Z]+$/
           )
        {
            *{"hidden::$cmethod"} = *{$cmethod}{CODE};
            *{$cmethod} = sub {
                my $err = &{"hidden::$cmethod"};
                if("$err")
                {
                    Image::Magick::Exception->throw (error => "$err");
                };
                $err;
             };
        }
    }
}

package main;

use Image::Magick;
use Image::Magick::Exceptions;

etc();
[download]

As a proof of concept this works. BUT, things start going wrong when a function is *supposed* to return a string, like the Get/GetAttribute (why all these aliases, by the way?). Reading the documentation again, it says you need to handle methods differently based on what they are supposed to return.

   $ret = $image->Write;
   if ("$ret") { error("$ret") }
   print $ret . " images written";
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   $clone = $image->Clone;
   if (!ref $clone) { error($clone) }
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I could fix my Image::Magick::Exceptions module, by keeping a list of method names and return types.

But where to find these? Even the I::M manual is not clear on what methods return what. Or even fails to mention all methods.

And even this doesn't handle the warn()'s that I::M throws every now and then.

Finally, and thanks for bearing with my long winded post, the question:

Is there a better (non-documented) way to catch errors from I::M?
Or else, is there a better manual than the one provided with I::M?

--
Lyon