Access Impl field from closure before field is alloc'ed in Rust?

Question

I am new to Rust, as will probably be obvious.

Basically I have this scenario you can see below where, I create a new type that has a closure added to it, but this closure needs to access data which has not yet been created. The data will be created by the time the closure gets called, but when the closure is initially created the data is not yet available.

What is the best way to do deal with?

I am also curious if my closure was not a closure, but rather a private function in my implementation, how would I access that data? This closure/function is a callback from WasmTime and requires an explicit method signature which does not allow me to add $self to it. So how could I get at the instance fields of the implementation without a reference to $self in the function parameters?

pub struct EmWasmNode {
    wasmStore: Store<WasiCtx>,
    wasmTable: Table,
}

impl EmWasmNode {
    pub fn new(filePath: &str) -> Result<Self> {

        let engine = Engine::default();
        // let module = Module::from_file(&engine, "wasm/index.wast")?;
        let module = Module::from_file(&engine, filePath)?;
        let mut linker = Linker::new(&engine);
        wasmtime_wasi::add_to_linker(&mut linker, |s| s)?;

        let wasi = WasiCtxBuilder::new()
            .inherit_stdio()
            .inherit_args()?
            .build();
        let mut store = Store::new(&engine, wasi);

        linker.func_wrap("env", "emscripten_set_main_loop", |p0: i32, p1: i32, p2: i32| {
            println!("emscripten_set_main_loop {} {} {}", p0, p1, p2);
/*** How would I access wasmTable and wasmStore from here to execute more methods??? ***/

            //let browserIterationFuncOption:Option<wasmtime::Val> = Self::wasmTable.get(&mut Self::wasmStore, p0 as u32);
            // browserIterationFuncOption.unwrap().unwrap_funcref().call(&store, ());
        })?;

        let instance = linker.instantiate(&mut store, &module)?;

        let table = instance
            .get_export(&mut store, "__indirect_function_table")
            .as_ref()
            .and_then(extern_table)
            .cloned();

        let start = instance.get_typed_func::<(), (), _>(&mut store, "_start")?;

        start.call(&mut store, ())?;

        Ok(EmWasmNode {
            wasmStore: store,
            wasmTable: table.unwrap(),
        })
    }

Answer 1

You have to instantiate a struct before. I suggest the more simple code below to see my idea.

struct Atype
{
    name: String,
}

impl Atype
{
    pub fn new() -> Self
    {
        Self{ name: String::from("zeppi")}
    }
    
    pub fn test(&self) -> ()
    {
        let func = | x | { println!("{} {}", &self.name, x);};
        func(3)
    }
}

fn main() {
    let o = Atype::new();
    o.test();
}