How to implement around in Raku

Question

In Perl, using Moo, you can implement around subs, which will wrap around other methods in a class.

around INSERT => sub {
    my $orig = shift;
    my $self = shift;

    print "Before the original sub\n";
    my $rv  = $orig->($self, @_);
    print "After the original sub\n";
};

How can this behaviour be implemented in Raku, preferably using a role?

Answer 1

Use wrap

sub bar () { return "baþ" };

my $wrapped = &bar.wrap( { " → " ~ callsame() ~ " ← " } );

say bar(); # OUTPUT:  «→ baþ ← »

Since methods are routines, you'll need a slightly more convoluted way to get a handle on the method itself, but other than that, the method is exactly the same, since Methods are a subclass of Routines

class Baz {
    method bar () { return "baþ" };
}

my &method_bar = Baz.^find_method("bar");
my $wrapped = &method_bar.wrap( { " → " ~ callsame() ~ " ← " } );

say Baz.bar(); # OUTPUT:  «→ baþ ← »

The $wrapped is a handle that can be used, later on, to unwrap it if needed.

Edit: to add the code to get a handle on the class method, taken from here, for instance.