how to use call dart from rust with my argument?

[Sherlock-Holo]

I am reading the doc and I notice frb v2 supports call dart codes from rust side https://cjycode.com/flutter_rust_bridge/guides/direction/rust-call-dart

however it make me confuse

rustFunction(dartCallback: (name) => 'Hello, $name!');

that may mean set the callback in dart codes, so rust side can call it

but in rust side

pub fn rust_function(dart_callback: Fn(String) -> String) {
    dart_callback("Tom"); // Will get `Hello, Tom!`
}

well I don't know how to use this function

// other codes

rust_function(???where can I find the closure???)

or should I use something generated by frb?

and

if I want to pass my name variable to dart side, how to do it?

let name = "test".to_string();

// how to pass the variable as argument to function???

[fzyzcjy]

Hi, I am not very sure about the question. Could you please elaborate a bit more?

To be more explicitly, in case it helps:

pub fn rust_function(dart_callback: Fn(String) -> String) {
    let name = "test".to_string();
    dart_callback(name); // <-- answer your last question
}

void thisIsDartFunction(String name) { print('hi $name'); } // this is a dart function

rustFunction(dartCallback: thisIsDartFunction); // you can pass the dart function as an argument to Rust

[Sherlock-Holo]

oh I misunderstood the example

I thought

rustFunction(dartCallback: (name) => 'Hello, $name!');

meant dart provide a ffi function directly, like

fn my_rust_function(a: String) -> String { a.repeat(2) }

but actually: rust provide a function that allow dart call rust function to pass a callback to rust side, then rust can store the callback, and invoke the callback later to achieve the purpose of calling the dart codes