Reusing signal handlers? - vala

Question

Is there a way in Vala to have multiple signal handlers perform the same code, while they have access to the local scope?
Defining a lambda using a delegate works, but requires a delegate definition and gives the warning "copying delegates is not supported":
delegate void ChangeHandler ();
void test () {
var answer = 42;
ChangeHandler handler = () => {
debug("size or position changed. answer: %i", answer);
};
size_changed.connect (handler);
position_changed.connect (handler);
}
As far as I know there is also no way to pass information to handlers? something like:
void test () {
var answer = 42;
size_changed.connect (handler, answer);
position_changed.connect (handler, answer);
}
void handler (answer) {
debug("size or position changed. answer: %i", answer);
}
I could do this, but this requires a lot of extra code, especially when there are many arguments.
void test () {
var answer = 42;
size_changed.connect (handler, answer);
position_changed.connect (() => handler(answer));
}
void handler (answer) {
debug("size or position changed. answer: %i", answer);
}
Is there a way to connect multiple signals to one anonymous function? Something like:
void test () {
var answer = 42;
multi_connect(size_changed, position_changed, () => {
debug("size or position changed. answer: %i", answer);
});
}

Answer 1

How about using this to pass data:
public class Test : GLib.Object {
public signal void sig_1 ();
public signal void sig_2 ();
private int answer = 42;
private void sig_handler (Test t) {
stdout.printf("sig_1 or sig_2 triggered. answer: %d\n", answer);
}
public static int main(string[] args) {
Test t1 = new Test();
t1.sig_1.connect(t1.sig_handler);
t1.sig_2.connect(t1.sig_handler);
t1.sig_1();
t1.sig_2();
return 0;
}
}
Maybe it is more readable with two classes:
public class SignalRaiser : GLib.Object {
public signal void sig_1 ();
public signal void sig_2 ();
}
public class SignalReceiver : GLib.Object {
private int answer = 42;
public void sig_handler (SignalRaiser sender) {
stdout.printf("sig_1 or sig_2 triggered. answer: %d\n", answer);
}
}
int main(string[] args) {
var raiser = new SignalRaiser();
var receiver = new SignalReceiver();
raiser.sig_1.connect(receiver.sig_handler);
raiser.sig_2.connect(receiver.sig_handler);
raiser.sig_1();
raiser.sig_2();
return 0;
}