Mojo::Exception(3pm) User Contributed Perl Documentation Mojo::Exception(3pm)
NAME
Mojo::Exception - Exception base class
SYNOPSIS
# Create exception classes
package MyApp::X::Foo {
use Mojo::Base 'Mojo::Exception';
}
package MyApp::X::Bar {
use Mojo::Base 'Mojo::Exception';
}
# Throw exceptions and handle them gracefully
use Mojo::Exception qw(check);
eval {
MyApp::X::Foo->throw('Something went wrong!');
};
check $@ => [
'MyApp::X::Foo' => sub { say "Foo: $_" },
'MyApp::X::Bar' => sub { say "Bar: $_" }
];
# Generate exception classes on demand
use Mojo::Exception qw(check raise);
eval {
raise 'MyApp::X::Name', 'The name Minion is already taken';
};
check $@ => [
'MyApp::X::Name' => sub { say "Name error: $_" },
default => sub { say "Error: $_" }
];
DESCRIPTION
Mojo::Exception is a container for exceptions with context information.
FUNCTIONS
Mojo::Exception implements the following functions, which can be
imported individually.
check
my $bool = check $err => ['MyApp::X::Foo' => sub {...}];
Process exceptions by dispatching them to handlers with one or more
matching conditions. Exceptions that could not be handled will be
rethrown automatically. Note that this function is EXPERIMENTAL and
might change without warning!
# Handle various types of exceptions
eval {
dangerous_code();
};
check $@ => [
'MyApp::X::Foo' => sub { say "Foo: $_" },
qr/^Could not open/ => sub { say "Open error: $_" },
default => sub { say "Something went wrong: $_" }
];
Matching conditions can be class names for ISA checks on exception
objects, or regular expressions to match string exceptions and
stringified exception objects. The matching exception will be the first
argument passed to the callback, and is also available as $_.
# Catch MyApp::X::Foo object or a specific string exception
eval {
dangerous_code();
};
check $@ => [
'MyApp::X::Foo' => sub { say "Foo: $_" },
qr/^Could not open/ => sub { say "Open error: $_" }
];
An array reference can be used to share the same handler with multiple
conditions, of which only one needs to match. And since exception
handlers are just callbacks, they can also throw their own exceptions.
# Handle MyApp::X::Foo and MyApp::X::Bar the same
eval {
dangerous_code();
};
check $@ => [
['MyApp::X::Foo', 'MyApp::X::Bar'] => sub { die "Foo/Bar: $_" }
];
There is currently only one keywords you can use to set special
handlers. The "default" handler is used when no other handler matched.
# Use "default" to catch everything
eval {
dangerous_code();
};
check $@ => [
default => sub { say "Error: $_" }
];
raise
raise 'Something went wrong!';
raise 'MyApp::X::Foo', 'Something went wrong!';
Raise a Mojo::Exception, if the class does not exist yet (classes are
checked for a "new" method), one is created as a Mojo::Exception
subclass on demand. Note that this function is EXPERIMENTAL and might
change without warning!
ATTRIBUTES
Mojo::Exception implements the following attributes.
frames
my $frames = $e->frames;
$e = $e->frames([$frame1, $frame2]);
Stack trace if available.
# Extract information from the last frame
my ($package, $filename, $line, $subroutine, $hasargs, $wantarray, $evaltext,
$is_require, $hints, $bitmask, $hinthash) = @{$e->frames->[-1]};
line
my $line = $e->line;
$e = $e->line([3, 'die;']);
The line where the exception occurred if available.
lines_after
my $lines = $e->lines_after;
$e = $e->lines_after([[4, 'say $foo;'], [5, 'say $bar;']]);
Lines after the line where the exception occurred if available.
lines_before
my $lines = $e->lines_before;
$e = $e->lines_before([[1, 'my $foo = 23;'], [2, 'my $bar = 24;']]);
Lines before the line where the exception occurred if available.
message
my $msg = $e->message;
$e = $e->message('Died at test.pl line 3.');
Exception message, defaults to "Exception!".
verbose
my $bool = $e->verbose;
$e = $e->verbose($bool);
Show more information with "to_string", such as "frames", defaults to
the value of the "MOJO_EXCEPTION_VERBOSE" environment variable.
METHODS
Mojo::Exception inherits all methods from Mojo::Base and implements the
following new ones.
inspect
$e = $e->inspect;
$e = $e->inspect($source1, $source2);
Inspect "message", "frames" and optional additional sources to fill
"lines_before", "line" and "lines_after" with context information.
new
my $e = Mojo::Exception->new;
my $e = Mojo::Exception->new('Died at test.pl line 3.');
Construct a new Mojo::Exception object and assign "message" if
necessary.
to_string
my $str = $e->to_string;
Render exception. Note that the output format may change as more
features are added, only the error message at the beginning is
guaranteed not to be modified to allow regex matching.
throw
Mojo::Exception->throw('Something went wrong!');
Throw exception from the current execution context.
# Longer version
die Mojo::Exception->new('Something went wrong!')->trace;
trace
$e = $e->trace;
$e = $e->trace($skip);
Generate stack trace and store all "frames", defaults to skipping 1
call frame.
# Skip 3 call frames
$e->trace(3);
# Skip no call frames
$e->trace(0);
OPERATORS
Mojo::Exception overloads the following operators.
bool
my $bool = !!$e;
Always true.
stringify
my $str = "$e";
Alias for "to_string".
SEE ALSO
Mojolicious, Mojolicious::Guides, <https://mojolicious.org>.
perl v5.36.0 2022-12-22 Mojo::Exception(3pm)
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