Giter VIP home page Giter VIP logo

Comments (1)

spookyvision avatar spookyvision commented on May 27, 2024

since I needed this I've hacked something together (mostly copy-paste of dioxus code, plus one argument) that appears to work for me. Let me know if this looks plausible and if so I'll create a PR!

pub fn use_callback1<T, O>(f: impl FnMut(T) -> O + 'static) -> UseCallback1<O, T> {
    // Create a copyvalue with no contents
    // This copyvalue is generic over F so that it can be sized properly
    let mut inner = use_hook(|| CopyValue::new(None));

    // Every time this hook is called replace the inner callback with the new callback
    inner.set(Some(f));

    // And then wrap that callback in a boxed callback so we're blind to the size of the actual callback
    use_hook(|| {
        let cur_scope = current_scope_id().unwrap();
        let rt = Runtime::current().unwrap();

        UseCallback1 {
            inner: CopyValue::new(Box::new(move |arg1| {
                // run this callback in the context of the scope it was created in.
                let run_callback = || inner.with_mut(|f: &mut Option<_>| f.as_mut().unwrap()(arg1));
                rt.on_scope(cur_scope, run_callback)
            })),
        }
    })
}

/// This callback is not generic over a return type so you can hold a bunch of callbacks at once
///
/// If you need a callback that returns a value, you can simply wrap the closure you pass in that sets a value in its scope
#[derive(PartialEq)]
pub struct UseCallback1<O: 'static + ?Sized, T: 'static> {
    inner: CopyValue<Box<dyn FnMut(T) -> O>>,
}

impl<O: 'static + ?Sized, T> Clone for UseCallback1<O, T> {
    fn clone(&self) -> Self {
        Self { inner: self.inner }
    }
}
impl<O: 'static, T: 'static> Copy for UseCallback1<O, T> {}

impl<O, T> UseCallback1<O, T> {
    /// Call the callback
    pub fn call(&self, arg1: T) -> O {
        (self.inner.write_unchecked())(arg1)
    }
}

// This makes UseCallback callable like a normal function
impl<O, T> std::ops::Deref for UseCallback1<O, T> {
    type Target = dyn Fn(T) -> O;

    fn deref(&self) -> &Self::Target {
        // https://github.com/dtolnay/case-studies/tree/master/callable-types

        // First we create a closure that captures something with the Same in memory layout as Self (MaybeUninit<Self>).
        let uninit_callable = MaybeUninit::<Self>::uninit();
        // Then move that value into the closure. We assume that the closure now has a in memory layout of Self.
        let uninit_closure = move |arg1| Self::call(unsafe { &*uninit_callable.as_ptr() }, arg1);

        // Check that the size of the closure is the same as the size of Self in case the compiler changed the layout of the closure.
        let size_of_closure = std::mem::size_of_val(&uninit_closure);
        assert_eq!(size_of_closure, std::mem::size_of::<Self>());

        // Then cast the lifetime of the closure to the lifetime of &self.
        fn cast_lifetime<'a, T>(_a: &T, b: &'a T) -> &'a T {
            b
        }
        let reference_to_closure = cast_lifetime(
            {
                // The real closure that we will never use.
                &uninit_closure
            },
            // We transmute self into a reference to the closure. This is safe because we know that the closure has the same memory layout as Self so &Closure == &Self.
            unsafe { std::mem::transmute(self) },
        );

        // Cast the closure to a trait object.
        reference_to_closure as &_
    }
}

from dioxus.

Related Issues (20)

Recommend Projects

  • React photo React

    A declarative, efficient, and flexible JavaScript library for building user interfaces.

  • Vue.js photo Vue.js

    🖖 Vue.js is a progressive, incrementally-adoptable JavaScript framework for building UI on the web.

  • Typescript photo Typescript

    TypeScript is a superset of JavaScript that compiles to clean JavaScript output.

  • TensorFlow photo TensorFlow

    An Open Source Machine Learning Framework for Everyone

  • Django photo Django

    The Web framework for perfectionists with deadlines.

  • D3 photo D3

    Bring data to life with SVG, Canvas and HTML. 📊📈🎉

Recommend Topics

  • javascript

    JavaScript (JS) is a lightweight interpreted programming language with first-class functions.

  • web

    Some thing interesting about web. New door for the world.

  • server

    A server is a program made to process requests and deliver data to clients.

  • Machine learning

    Machine learning is a way of modeling and interpreting data that allows a piece of software to respond intelligently.

  • Game

    Some thing interesting about game, make everyone happy.

Recommend Org

  • Facebook photo Facebook

    We are working to build community through open source technology. NB: members must have two-factor auth.

  • Microsoft photo Microsoft

    Open source projects and samples from Microsoft.

  • Google photo Google

    Google ❤️ Open Source for everyone.

  • D3 photo D3

    Data-Driven Documents codes.