use_state in Yew

Question

I am new to Rust and Yew and I need some assistance in applying a useState hook inside an app component in Yew that looks like this:

struct BookList
use gloo_net::http::Request;    
use yew::prelude::*;

#[function_component(App)]
pub fn app() -> Html {
    let (books: UseStateHandle<Vec<BookList>> = use_state(|| vec![]);
    async fn fetch_books() {
        let response: Vec<> = Request::get("http://localhost:3000/books");
        let cloned_books = books.clone():
        cloned_books.set(response.data);
    }
    html! {
        <div>
            {"App"}
        </div>
    }
}

I got the error mismatched types. Where I have the parens, it says it expected a struct UseStateHandle, found tuple.

Answer 1

I'm not sure why you need an open bracket before books but I assume that this is where the confusion with the tuple comes from.

let books = use_state(|| vec![]);

If you assign the type when you fetch the data I am speculating that Rust should be smart enough to understand from the later context that this should be a handle to a vector of BookList. Thus, I would assign the type there (which you already almost had but it was missing the type):

let response: Vec<BookList> = Request::get("http://localhost:3000/books");

Note that I have not tried these. Feel free to comment with follow-up exceptions so we can together elaborate.