How to call a method within a `signal` block?

Question

Is it possible to call a user defined method within a signal block?

method my-method ( ... ) {
    signal(SIGTERM,SIGINT,SIGQUIT,SIGHUP).tap( -> $sig {
        say "Received signal: $sig";
        self!restore-term();
        exit;
    } );
    ...
    ...
}

Answer 1

Yes, but there are caveats.

signal provides a Supply of events, which you can tap (if you like to) but probably should be using inside a react whenever structure.

In your example, the tap takes a Block (lambda). Every time you call the method, it will set up another Supply (which is probably not what you want).

This block gets called whenever an event arrives. This means it is completely asynchronous and has no context, other than the lexical context in which the block was created.

So whenever a signal arrives in the Supply, it will run the block with the self at the moment the method got called. Which may not be what you expect?

So it feels to me you're asking the wrong question. Apparently you have an object (hopefully a sentinel) that you wish the restore-term method to be called on whenever someone indicates they want to leave the program. So you're probably better of restructuring your program to something like:

my $sentinel = class.new(...);
react {
    whenever signal(SIGTERM,SIGINT,SIGQUIT,SIGHUP) -> $sig {
        say "Received signal: $sig";
        $sentinel.restore-term();
        exit;
    }
    # .... other stuff
}