signals.md

Signals

Leveraging TypeScript's strong type checking, when you connect an incorrect callable object to a signal, the code editor will directly prompt you about the error.

Callable

Callable.create returns a Callable object.

Note

Since v0.9.8, the function callable from module godot-jsb is deprecated. Please directly use the static function create in Callable from module godot.

Warning

Please be cautious that Callable.create(this, this.xxx) === Callable.create(this, this.xxx) returns false.
But it's compared internally in C++ to check equality when using them for connect and disconnect.

import { Node, Callable } from "godot";

class MyClass extends Node {
    foo() {
        // subscribe
        this.onclick.connect(Callable.create(this, this.handle_onclick), 0);

        // unsubscribe
        this.onclick.disconnect(Callable.create(this, this.handle_onclick));
    }
}

Warning

Callable does not hold a strong reference on this which given as the first parameter. It becomes invalid after the corresponding javascript object is garbage collected.
HOWEVER, it may cause object leaks if this is captured in a lambda function. So avoid coding in this way Callable.create(this, () => this.xxx()).

Await a Signal

Signal can be awaitable in javascript by calling as_promise():

import { Node, Signal1 } from "godot";
import { signal } from "godot.annotations";

class ExampleClass extends Node {
    @signal()
    test_signal!: Signal1<number>;

    _ready() {
        test();
    }

    async test() {
        console.log("before signal emit");
        // result is 123
        const result = await this.test_signal.as_promise(); 
        console.log("after signal emit", result);
    }

    emit_somehow() {
        this.test_signal.emit(123);
    }
}

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