I've worked out how to do it, by adding a custom dispatch:<.?> method:
use Test;
class C {
method foo { 42 }
method can($meth-name) {
my $meths = callsame;
if !$meths && $meth-name eq 'bar' {
$meths = [method { 69 }, ];
self.^add_method($meth-name, $meths[0]);
}
$meths;
}
method dispatch:<.?>(\name, |c) is raw {
self.can(name)
?? self."{name}"(|c)
!! Nil
}
method FALLBACK(\name, |c) {
if self.can(name) {
self."{name}"(|c);
}
else {
die X::Method::NotFound.new( :method(name),
:typename(self.^name) );
}
}
}
for C {
my $obj = .new;
is $obj.foo, 42, 'static method - direct call';
is $obj.?foo, 42, 'static method - safe call';
is $obj.bar, 69, 'dynamic method - direct call';
is $obj.?bar, 69, 'dynamic method - safe call';
dies-ok {$obj.unknown}, 'direct call - unknown method dies';
lives-ok {$obj.?unknown}, 'safe call - unknown method lives';
}
Based on some code I found in the core Rakudo Mu class.
Slightly awkward, but at least working.
On Tue, Oct 18, 2016 at 1:35 PM, David Warring <perl6-bugs-follo...@perl.org
> wrote:
> # New Ticket Created by David Warring
> # Please include the string: [perl #129907]
> # in the subject line of all future correspondence about this issue.
> # <URL: https://rt.perl.org/Ticket/Display.html?id=129907 >
>
>
> I'm adding a FALLBACK method to create method dynamically, the it receives
> both '.' and '.?' invocations, and I can't distinguish between them.
>
> This then breaks $obj.unknown vs $obj.?unknown handling in class objects.
>
> Consider:
>
> use Test;
>
> class C {
> method foo { 42 }
> method FALLBACK($meth-name, |c) {
> warn "can $meth-name";
> if $meth-name eq 'bar' {
> self.^add_method($meth-name, method { 69 });
> self."$meth-name"(|c);
> }
> else {
> warn "dunno if this is a safe method call or not";
> Nil;
> }
> }
> }
>
> for C {
> my $obj = .new;
> is $obj.foo, 42, 'static method - direct call';
> is $obj.?foo, 42, 'static method - safe call';
> is $obj.bar, 69, 'dynamic method - direct call';
> is $obj.?bar, 69, 'dynamic method - safe call';
> todo "can't get both of these to pass!";
> dies-ok {$obj.unknown}, 'direct call - unknown method dies';
> lives-ok {$obj.?unknown}, 'safe call - unknown method lives';
> }
>
> I'm receiving both the safe and unsafe 'unknown' invocations, and can't
> distinguish them.
>
> I also tried overriding the classes 'can' method:
>
> class C {
> method foo { 42 }
> method can($meth-name) {
> my $meths = callsame;
> if !$meths && $meth-name eq 'bar' {
> $meths = [method { 69 }, ];
> self.^add_method($meth-name, $meths[0]);
> }
> $meths;
> }
> method FALLBACK($meth-name, |c) {
> if self.can($meth-name) {
> self."$meth-name"(|c);
> }
> else {
> warn "dunno if this is a safe method call or not";
> Nil;
> }
> }
> }
>
> But the FALLBACK is still needed, and still has the same problem.
>
> Any ideas?
>
