Add support for scoped contexts

[intendednull]

Primarily important for SSR support, containing state to the scope of the app, instead of the thread.

For a basic example, you can now create a local context for your dispatch:

#[derive(Clone, PartialEq, Default, Store)]
struct Counter(u32);

let cx = yewdux::Context::new();
let dispatch = Dispatch::<Counter>::new(&cx);

Changes to one context are not reflected in any others:

let cx_1 = yewdux::Context::new();
let dispatch_1 = Dispatch::<Counter>::new(&cx_1);

let cx_2 = yewdux::Context::new();
let dispatch_2 = Dispatch::<Counter>::new(&cx_2);

dispatch_1.set(Counter(1));
dispatch_2.set(Counter(2));

assert_ne!(dispatch_1.get(), dispatch_2.get());

The default context for a dispatch is global (thread local).

let dispatch_1 = Dispatch::<Counter>::global();
// This is equivalent to above.
let dispatch_2 = Dispatch::<Counter>::new(&yewdux::Context::global());

dispatch_1.set(Counter(1));

assert_eq!(dispatch_1.get(), dispatch_2.get());

A root component is now available to provide context that is scoped to the app:

use yew::prelude::*;
use yewdux::prelude::*;

#[derive(Default, Clone, PartialEq, Eq, Store)]
struct State {
    count: u32,
}

#[function_component]
fn Counter() -> Html {
    let (state, dispatch) = use_store::<State>();
    let onclick = dispatch.reduce_mut_callback(|state| state.count += 1);
    html! {
        <>
        <p>{ state.count }</p>
        <button {onclick}>{"+1"}</button>
        </>
    }
}

#[function_component]
fn App() -> Html {
    html! {
        <YewduxRoot>
            <Counter />
        </YewduxRoot>
    }
}

Hooks will detect the context provided by YewduxRoot. If no root is provided, it uses global by default.

[Roba1993]

I just went by this PR and I really like it and would also help me for specific cases. I could use them instead of the yew OOTB use_store hooks, which unfortunately have no reducer functions....

Ebenso I like the new feature I'm strongly argue to not change the actual api for the Dispatcher. This would break my code at 300+ places...
I mean this function:

let dispatch = Dispatch::<Counter>::new(&cx);

I would rather propose to keep the new function as it is and have an additional function like this:

let dispatch = Dispatch::<Counter>::ctx(&cx);

I also don't understand the benefit of an App vs Thread context. But this is definitely on me.

I hope, this feedback helps :)

[intendednull]

@Roba1993 thanks for the feedback!

I like the new feature I'm strongly argue to not change the actual api for the Dispatcher. This would break my code at 300+ places...

Hopefully you can refactor easily with a little regex magic. We aren't 1.0 yet, so breaking changes are to be expected, and shouldn't get in the way of improving the API.

I think this new naming scheme makes it super clear to the user when exactly they are accessing global context. It's a topic that may introduce confusion to newcomers, and so vitally important we make it as easy to understand as possible.

[Roba1993]

Hopefully you can refactor easily with a little regex magic. We aren't 1.0 yet, so breaking changes are to be expected, and shouldn't get in the way of improving the API.

I think this new naming scheme makes it super clear to the user when exactly they are accessing global context. It's a topic that may introduce confusion to newcomers, and so vitally important we make it as easy to understand as possible.

Yes, I will be able to do this 😄