[feature request] New API for FnPtr::call

[yunfengzh]

use rhai::{CallFnOptions, Dynamic, Engine, EvalAltResult, FnPtr, Scope};

const SCRIPT: &str = r#"
    fn init() {
        let my_handler = #{
            count: 0,
            on_player_joined: |event| {
                print(`got ${event}`);
                print(`now ${this.count}`);
            },
        };
        true
    }
"#;

fn main() -> Result<(), Box<EvalAltResult>> {
    let mut engine = Engine::new();
    engine.set_max_call_levels(64);
    engine.set_max_expr_depths(64, 64);
    let ast = engine.compile(SCRIPT)?;
    let mut scope = Scope::new();
    let options = CallFnOptions::new().eval_ast(false).rewind_scope(false);
    let _: bool = engine.call_fn_with_options(options, &mut scope, &ast, "init", ())?;

    let my_handler: Dynamic = scope.get_value("my_handler").unwrap();
    let binding = my_handler.as_map_ref().unwrap();
    let opj: FnPtr = binding.get("on_player_joined").unwrap().clone_cast();
    let _: bool = opj.call(&engine, &ast, (1_i64,))?; // <-- failed with Unboundthis error!

    Ok(())
}

I hope to inject an event from rust to rhai by above code which is, I think, better than current official solution. But I got an error ErrorUnboundThis when call FnPtr::call, so I hope a new API FnPtr::call(my_handler, ...) to achieve it. Thanks!

[schungx]

I see your point. You'd like to bind the this pointer on the call.

Currently you can probably do that by taking apart the FnPtr, extracting the name and the curried arguments. Then use call_fn. Yes it is a bit convoluted but you can make a function out of it.

[schungx]

Also, can you use FnPtr::call_raw?

[yunfengzh]

But how to construct NativeCallContext param of FnPtr::call_raw? NativeCallContext::new() has been deprecated and there is not sample about how to use it?

[schungx]

You can check the source for FnPtr::call which creates the context.

You may need to enable the internals feature though.

I do agree that having a dedicated call would be more proper... But you'd need to wait for the next version.