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

jsb.callable returns a Callable javascript object.

Warning

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

import { Node } from "godot";
import * as jsb from "godot-jsb";

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

        // unsubscribe
        this.onclick.disconnect(jsb.callable(this, this.handle_onclick));
    }
}

Note

jsb.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.

Warning

However, it may cause object leaks if this is captured in a lambda function. So avoid coding in this way jsb.callable(this, () => this.xxx()).

Await a Signal

With a simple wrapper, Signal can be awaitable in javascript:

import { Node, Signal } from "godot";
import { $wait, signal } from "jsb.core";

class ExampleClass extends Node {
    @signal()
    test_signal!: Signal;

    _ready() {
        test();
    }

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

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

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