Re: Blessing with unknown classnames

There is no requirement for $class to be a real class, have length, or even be present. See bless for details.

The use of ref in your posted code is not the best choice: the doco explains issues. It would be much better to use the blessed function of the builtin module Scalar::Util.

Here's an example of usage. My perle alias captures all sorts of problems.

$ alias perle
alias perle='perl -Mstrict -Mwarnings -Mautodie=:all -MCarp::Always -E
+'
[download]

$ perle '
    use Scalar::Util "blessed";

    for (1, 2) {
        say "Run: $_";
        my $ret = foo();
        my $err = blessed $ret;

        if (defined $err) {
            say qq{Error "$err" detected};
            say qq{Code: $ret->[0]};
            say qq{Errstr: $ret->[1]};
        }
        else {
            say qq{Success!};
            say for @$ret;
        }
    }

    sub foo {
        state $error = 0;
        my $retval;

        if ($error) {
            $retval = bless [0, "error was ..."] => "YouveGotError";
        }
        else {
            $retval = [42, 43];
        }

        $error ^= 1;
        return $retval;
    }
'
Run: 1
Success!
42
43
Run: 2
Error "YouveGotError" detected
Code: 0
Errstr: error was ...
[download]

[Note: Between reading the OP and clicking "Comment on", there appears to have been two updates to the OP. There may be others. I'm replying to the post that ended with "Thanks LanX for looking this up on CB". I don't believe this changes the essence of my reply; just bear in mind what I'm replying to.]

— Ken

Comment on Re: Blessing with unknown classnames Select or Download Code

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Re^2: Blessing with unknown classnames by bliako (Monsignor) on Apr 01, 2021 at 18:19 UTC
Hello Ken, Minor issue: finding the classname (e.g. `ref($ret)`) is part of deciding if sub returned an error, for example when sub normally returns a blessed object instead of unblessed ref (as in my example). apropos the edits: Yes, I have added another use-case 5 minutes after posting, sorry. It does not change anything in your post.	[reply] [d/l]
Re^3: Blessing with unknown classnames by kcott (Archbishop) on Apr 01, 2021 at 18:55 UTC
"Minor issue: finding the classname (e.g. `ref($ret)`) is part of deciding if sub returned an error, for example when sub normally returns a blessed object instead of unblessed ref (as in my example)." Sorry, but I don't understand this. My code using `blessed` clearly distinguished "Error" from "Success". Your line: `die "@$ret" if ref($ret) eq 'YouveGotError';` [download] could be rewritten as: `die "@$ret" if $err eq 'YouveGotError';` [download] If I change '`blessed $ret`' in my code, to '`ref $ret`', the output becomes: `Run: 1 Error "ARRAY" detected Code: 42 Errstr: 43 Run: 2 Error "YouveGotError" detected Code: 0 Errstr: error was ...` [download] which, I'm pretty sure, is not what you want. I suspect we may be talking at cross-purposes, or there's some other misunderstanding; however, I've looked back over our posts, and can't see what the problem might be. "apropos the edits: ..." No need to apologise. I just wanted to make it clear what I was responding to. There was no intended rebuke or other negativity. — Ken	[reply] [d/l] [select]
Re^4: Blessing with unknown classnames by bliako (Monsignor) on Apr 01, 2021 at 19:42 UTC
I mean this: `if (defined $err)` can become `if (defined($err) && ($err eq 'YouveGotError'))`, so that it errors only on'YouveGotError' blessed refs and nothing else, because the sub may normally return other blessed things.	[reply] [d/l] [select]
Re^5: Blessing with unknown classnames by haukex (Archbishop) on Apr 02, 2021 at 09:32 UTC
Re^6: Blessing with unknown classnames by bliako (Monsignor) on Apr 02, 2021 at 11:12 UTC
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