struct Event {
    sparam string
}
struct EventCallback{
   func fn(Event)
}
struct Emitter {
mut:
    listeners []EventCallback
}
//////////////////////////////////////////////////////
pub fn (e Event) str() string { return 'event{ $e.sparam }' }
pub fn (ec &EventCallback) str() string { return 'event_callback{ ' + ptr_str(ec.func) + ' }' }
pub fn new_emitter() Emitter {
    return Emitter{}
}
pub fn (e mut Emitter) connect(f fn(Event)) {
    e.listeners << EventCallback{ f }
}
pub fn (e Emitter) emit( sparam string) {
    event := Event{ sparam }
    println('emitting event: $event ...')
    for listener in e.listeners {
        f := listener.func
        f(event)
    }
}
//////////////////////////////////////////////////////
fn cb1(e Event){ println('cb1: $e') }
fn cb2(e Event){ println('cb2: $e') }

fn main(){
    mut ready_emitter := new_emitter()
    ready_emitter.connect( cb1 )
    ready_emitter.connect( cb2 )
    ready_emitter.emit('Hello')
}

/* produces:
-------------------------------------------------
emitting event: event{ Hello }  ...
cb1: event{ Hello }
cb2: event{ Hello }
*/