Hi everyone,

First of all, apologies for my extremely late reply, I'm working on this in my free time and I haven't had a chance to get back to it until now.

So below is the logic I am now using, and it seems to work: the function "strify" takes a value, produces the warnings / errors that I wanted to provide for user-friendliness, and otherwise should act like normal Perl stringification. If I wasn't providing those custom warning and error messages, the whole thing could be simplified quite a bit, that's something I'll consider for the next version. You can see the code (with detailed comments) in my module here. In researching a solution I ended up writing a bunch of test classes and test cases. 

#!/usr/bin/perl
use strict;
use warnings;

{   package OnlyAString;
    use overload fallback=>0,     '""'=>sub { ${shift()} }  }
{   package ICanStringify;
    use overload fallback=>undef, '0+'=>sub { ${shift()} }  }
{   package OnlyANumber;
    use overload fallback=>0,     '0+'=>sub { ${shift()} }  }

print "  OnlyAString: ",strify(bless \do {my $x=111}, 'OnlyAString'  )
+,"\n";
print "ICanStringify: ",strify(bless \do {my $x=222}, 'ICanStringify')
+,"\n";
print "  OnlyANumber: ",strify(bless \do {my $x=333}, 'OnlyANumber'  )
+,"\n";

use Scalar::Util 'blessed';
use overload ();
use Carp;
sub strify {
    my ($x) = @_;
    if (!defined $x) {
        warnings::warnif('uninitialized','Use of uninitialized value i
+n argument list');
        return "" }
    elsif (blessed($x) && overload::Overloaded($x)) {
        if (overload::Method($x,'""'))  # we can assume stringify will
+ work
            { return "$x" }
        elsif (defined(my $rv = eval { "$x" }))
            { return $rv }
        elsif ($@=~/\bno method found\b/)  # throw custom error messag
+e
            { croak "Package ".ref($x)." doesn't overload stringificat
+ion: $@" }
        else { die $@ }
    }
    else {
        ref($x) and warnings::warnif("Argument list contains reference
+s/objects");
        return "$x" }
}

[download]

Output: 

  OnlyAString: 111
ICanStringify: 222
Package OnlyANumber doesn't overload stringification: Operation """": 
+no method found, argument in overloaded package OnlyANumber at ...

[download]

Thanks and Regards,
-- Hauke D

In reply to Re: Can I ask Perl if an object will stringify? by haukex
in thread Can I ask Perl if an object will stringify? by haukex

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