How to call use_effect?

[ChocolateLoverRaj]

This is my attempt:

use wasm_react::{
    h,
    hooks::{use_effect, use_state, Deps},
    Component, VNode,
};

pub struct CanCamera;

impl Component for CanCamera {
    fn render(&self) -> VNode {
        use_state(|| false);
        use_effect(|| println!("hi"), Deps::none());
        h!(h1).build("can camera")
    }
}

but I get this error:

expected a `FnOnce<()>` closure, found `()`
the trait `FnOnce<()>` is not implemented for `()`
wrap the `()` in a closure with no arguments: `|| { /* code */ }`rustc[Click for full compiler diagnostic](rust-analyzer-diagnostics-view:/diagnostic%20message%20%5B0%5D?0#file%3A%2F%2F%2Fvar%2Fhome%2Frajas%2FDocuments%2Fraise-hand-ai-1%2Fsrc%2Fhand_raised%2Fcan_camera.rs)
use_effect.rs(78, 6): required by a bound in `use_effect`

[ChocolateLoverRaj]

After looking at the example in use_effect.rs, I figured out how to do it.

use wasm_react::{
    h,
    hooks::{use_effect, use_state, Deps},
    Component, VNode,
};
use web_sys::console::log_1;

pub struct CanCamera;

impl Component for CanCamera {
    fn render(&self) -> VNode {
        use_state(|| false);
        use_effect(
            {
                log_1(&"use effect function!".into());
                move || || ()
            },
            Deps::none(),
        );
        h!(h1).build("can camera")
    }
}

I'm guessing the move || || () is needed because use_effect in this crate requires a cleanup function. @yishn is this true?

[yishn]

You have to wrap your effect code in the closure and return a destructor (see also documentaiton):

use_effect(move || {
  log_1(&"...".into());

  || ()
}, Deps::none());

With v0.6 you do not need to return anything to imply a noop destructor || ():

use_effect(move || {
  log_1(&"...".into());
}, Deps::none());