How to pass a callback to a registered type function?

[RazrFalcon]

I saw examples of passing a callback from Rhai to Rust in the book, but they use global functions. I'm trying to implement something like this:

variable.do_stuff(|v| println(v));

[schungx]

Not very sure what you're looking for. There are multiple ways to call Rhai functions from Rust (consult the Book).

Depends on what you want to achieve. For example, you seem to be using Rhai scripts are event handlers (aka callbacks), and there is a usage pattern in the Book on this.

[RazrFalcon]

I'm basically looking for a way to write:

impl MyType {
    fn do_stuff(&mut self, callback: rhai::FnPtr) {
        callback.call_dynamic(); // where can I get `NativeCallContext` from?
    }
}

[schungx]

Try:

https://rhai.rs/book/rust/context.html https://rhai.rs/book/language/fn-ptr.html#nativecallcontext

[RazrFalcon]

Yes, I read the book. The problem is that I don't have an access to the engine from the type. And storing a copy of the engine (if this even possible) in each registered type seems like an overkill.

It seems like the only way is to have a global function and pass a type and a closure into it.

[schungx]

What's wrong with:

impl MyType {
    fn do_stuff(context: NativeCallContext, &mut self, callback: rhai::FnPtr) {
        callback.call_dynamic(context, ...);
    }
}

[RazrFalcon]

self must be the first argument. And it would not compile anyway:

error[E0277]: the trait bound `for<'r, 's> fn(&'r mut TestStruct, NativeCallContext<'s>, FnPtr) {TestStruct::do_stuff}: RegisterNativeFunction<_, ()>` is not satisfied
   --> src/lib.rs:562:34
    |
562 |         .register_fn("do_stuff", TestStruct::do_stuff)
    |                                  ^^^^^^^^^^^^^^^^^^^^ the trait `RegisterNativeFunction<_, ()>` is not implemented for `for<'r, 's> fn(&'r mut TestStruct, NativeCallContext<'s>, FnPtr) {TestStruct::do_stuff}`

[schungx]

fn do_stuff(context: NativeCallContext, obj: &mut MyType, callback: rhai::FnPtr) {
    callback.call_dynamic(context, ...);
}

engine.register_fn("do_stuff", do_stuff);

[RazrFalcon]

Thanks! This is what I was looking for.

[schungx]

Or simpler:

impl MyType {
    fn do_stuff(&mut self, context: NativeCallContext, callback: rhai::FnPtr) {
        callback.call_dynamic(context, ...);
    }
}

engine.register_fn("do_stuff", |context: NativeCallContext, obj: &mut MyType, callback: FnPtr| obj.do_stuff(context, callback));

However, if you have a context parameter, you may not really want that method into MyType in the first place...