make mapped signal readable

packages/signals/Cargo.toml

@@ -25,7 +25,7 @@ futures-util = { workspace = true }
 flume = { version = "0.11.0", default-features = false, features = ["async"] }
 
 [dev-dependencies]
-dioxus = { workspace = true }
+dioxus = { workspace = true, features = ["desktop"]}
 # dioxus-desktop = { workspace = true }
 tokio = { version = "1", features = ["full"] }
 tracing-subscriber = "0.3.17"

packages/signals/examples/map_signal.rs

@@ -0,0 +1,51 @@
+#![allow(non_snake_case)]
+
+use dioxus::prelude::*;
+use dioxus_signals::Signal;
+
+fn main() {
+    launch(app);
+}
+
+fn app() -> Element {
+    let mut vec = use_signal(|| vec![0]);
+
+    rsx! {
+        button {
+            onclick: move |_| {
+                let mut write = vec.write();
+                let len = write.len() as i32;
+                write.push(len);
+            },
+            "Create"
+        }
+
+        button {
+            onclick: move |_| {
+                vec.write().pop();
+            },
+            "Destroy"
+        }
+
+        for i in 0..vec.len() {
+            Child { count: vec.map(move |v| &v[i]) }
+        }
+    }
+}
+
+#[component]
+fn Child(count: MappedSignal<i32, Signal<Vec<i32>>>) -> Element {
+    use_memo({
+        to_owned![count];
+        move || {
+            let value = count.read();
+            print!("Child value: {value}");
+        }
+    });
+
+    rsx! {
+        div {
+            "Child: {count}"
+        }
+    }
+}

packages/signals/src/global/signal.rs

@@ -2,11 +2,11 @@ use crate::read::Readable;
 use crate::write::Writable;
 use crate::Write;
 use dioxus_core::prelude::{IntoAttributeValue, ScopeId};
-use generational_box::{AnyStorage, GenerationalRef, UnsyncStorage};
-use std::{cell::Ref, mem::MaybeUninit, ops::Deref};
+use generational_box::{AnyStorage, UnsyncStorage};
+use std::{mem::MaybeUninit, ops::Deref};
 
 use super::get_global_context;
-use crate::{MappedSignal, Signal};
+use crate::Signal;
 
 /// A signal that can be accessed from anywhere in the application and created in a static
 pub struct GlobalSignal<T> {
@@ -60,15 +60,6 @@ impl<T: 'static> GlobalSignal<T> {
         self.signal().with_mut(f)
     }
 
-    /// Map the signal to a new type.
-    pub fn map<O>(
-        &self,
-        f: impl Fn(&T) -> &O + 'static,
-    ) -> MappedSignal<GenerationalRef<Ref<'static, O>>> {
-        // MappedSignal::new(self.signal(), f)
-        todo!()
-    }
-
     /// Get the generational id of the signal.
     pub fn id(&self) -> generational_box::GenerationalBoxId {
         self.signal().id()

packages/signals/src/impls.rs

@@ -2,7 +2,7 @@ use crate::copy_value::CopyValue;
 use crate::read::Readable;
 use crate::signal::Signal;
 use crate::write::Writable;
-use crate::{GlobalMemo, GlobalSignal, ReadOnlySignal, SignalData};
+use crate::{GlobalMemo, GlobalSignal, MappedSignal, ReadOnlySignal, SignalData};
 use generational_box::Storage;
 
 use std::{
@@ -10,7 +10,7 @@ use std::{
     ops::{Add, Div, Mul, Sub},
 };
 
-macro_rules! read_impls {
+macro_rules! default_impl {
     ($ty:ident $(: $extra_bounds:path)? $(, $bound_ty:ident : $bound:path, $vec_bound_ty:ident : $vec_bound:path)?) => {
         $(
             impl<T: Default + 'static, $bound_ty: $bound> Default for $ty<T, $bound_ty> {
@@ -20,7 +20,11 @@ macro_rules! read_impls {
                 }
             }
         )?
+    }
+}
 
+macro_rules! read_impls {
+    ($ty:ident $(: $extra_bounds:path)? $(, $bound_ty:ident : $bound:path, $vec_bound_ty:ident : $vec_bound:path)?) => {
         impl<T: $($extra_bounds + )? Display + 'static $(,$bound_ty: $bound)?> Display for $ty<T $(, $bound_ty)?> {
             #[track_caller]
             fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
@@ -113,6 +117,7 @@ macro_rules! write_impls {
 }
 
 read_impls!(CopyValue, S: Storage<T>, S: Storage<Vec<T>>);
+default_impl!(CopyValue, S: Storage<T>, S: Storage<Vec<T>>);
 write_impls!(CopyValue, Storage<T>, Storage<Vec<T>>);
 
 impl<T: 'static, S: Storage<T>> Clone for CopyValue<T, S> {
@@ -124,6 +129,7 @@ impl<T: 'static, S: Storage<T>> Clone for CopyValue<T, S> {
 impl<T: 'static, S: Storage<T>> Copy for CopyValue<T, S> {}
 
 read_impls!(Signal, S: Storage<SignalData<T>>, S: Storage<SignalData<Vec<T>>>);
+default_impl!(Signal, S: Storage<SignalData<T>>, S: Storage<SignalData<Vec<T>>>);
 write_impls!(Signal, Storage<SignalData<T>>, Storage<SignalData<Vec<T>>>);
 
 impl<T: 'static, S: Storage<SignalData<T>>> Clone for Signal<T, S> {
@@ -139,6 +145,11 @@ read_impls!(
     S: Storage<SignalData<T>>,
     S: Storage<SignalData<Vec<T>>>
 );
+default_impl!(
+    ReadOnlySignal,
+    S: Storage<SignalData<T>>,
+    S: Storage<SignalData<Vec<T>>>
+);
 
 impl<T: 'static, S: Storage<SignalData<T>>> Clone for ReadOnlySignal<T, S> {
     fn clone(&self) -> Self {
@@ -149,5 +160,8 @@ impl<T: 'static, S: Storage<SignalData<T>>> Clone for ReadOnlySignal<T, S> {
 impl<T: 'static, S: Storage<SignalData<T>>> Copy for ReadOnlySignal<T, S> {}
 
 read_impls!(GlobalSignal);
+default_impl!(GlobalSignal);
 
 read_impls!(GlobalMemo: PartialEq);
+
+read_impls!(MappedSignal, S: Readable, S: Readable);

packages/signals/src/map.rs

@@ -1,107 +1,101 @@
+use std::{ops::Deref, rc::Rc};
+
 use crate::read::Readable;
-use crate::CopyValue;
-use crate::Signal;
-use crate::SignalData;
-use dioxus_core::ScopeId;
-use generational_box::AnyStorage;
-use generational_box::Storage;
-use generational_box::UnsyncStorage;
-use std::fmt::Debug;
-use std::fmt::Display;
+use dioxus_core::prelude::*;
 
 /// A read only signal that has been mapped to a new type.
-pub struct MappedSignal<U: ?Sized + 'static, S: AnyStorage = UnsyncStorage> {
-    mapping: CopyValue<Box<dyn Fn() -> S::Ref<U>>>,
+pub struct MappedSignal<O: ?Sized + 'static, R: Readable> {
+    readable: R,
+    mapping: Rc<dyn Fn(&R::Target) -> &O + 'static>,
 }
 
-impl MappedSignal<()> {
-    /// Create a new mapped signal.
-    pub fn new<R, T, S, U>(readable: R, mapping: impl Fn(&T) -> &U + 'static) -> MappedSignal<U, S>
-    where
-        S: Storage<SignalData<T>>,
-        U: ?Sized,
-    {
-        todo!()
-        // MappedSignal {
-        //     mapping: CopyValue::new(Box::new(move || S::map(signal.read(), &mapping))),
-        // }
+impl<O: ?Sized, R: Readable + Clone> Clone for MappedSignal<O, R> {
+    fn clone(&self) -> Self {
+        MappedSignal {
+            readable: self.readable.clone(),
+            mapping: self.mapping.clone(),
+        }
     }
 }
 
-// impl<U: ?Sized> MappedSignal<U> {
-//     /// Get the current value of the signal. This will subscribe the current scope to the signal.
-//     pub fn read(&self) -> U {
-//         (self.mapping.read())()
-//     }
-
-//     /// Run a closure with a reference to the signal's value.
-//     pub fn with<O>(&self, f: impl FnOnce(U) -> O) -> O {
-//         f(self.read())
-//     }
-// }
-
-// impl<U: ?Sized + Clone> MappedSignal<U> {
-//     /// Get the current value of the signal. This will subscribe the current scope to the signal.
-//     pub fn value(&self) -> U {
-//         self.read().clone()
-//     }
-// }
-
-// impl<U: ?Sized> PartialEq for MappedSignal<U> {
-//     fn eq(&self, other: &Self) -> bool {
-//         self.mapping == other.mapping
-//     }
-// }
-
-// impl<U> std::clone::Clone for MappedSignal<U> {
-//     fn clone(&self) -> Self {
-//         *self
-//     }
-// }
-
-// impl<U> Copy for MappedSignal<U> {}
-
-// impl<U: Display> Display for MappedSignal<U> {
-//     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-//         self.with(|v| Display::fmt(&v, f))
-//     }
-// }
+impl<O, R> MappedSignal<O, R>
+where
+    O: ?Sized,
+    R: Readable + 'static,
+{
+    /// Create a new mapped signal.
+    pub(crate) fn new(readable: R, mapping: impl Fn(&R::Target) -> &O + 'static) -> Self {
+        MappedSignal {
+            readable,
+            mapping: Rc::new(mapping),
+        }
+    }
+}
 
-// impl<U: Debug> Debug for MappedSignal<U> {
-//     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-//         self.with(|v| Debug::fmt(&v, f))
-//     }
-// }
+impl<O, R> Readable for MappedSignal<O, R>
+where
+    O: ?Sized,
+    R: Readable,
+{
+    type Target = O;
+    type Ref<J: ?Sized + 'static> = R::Ref<J>;
+
+    fn map_ref<I: ?Sized, U: ?Sized, F: FnOnce(&I) -> &U>(
+        ref_: Self::Ref<I>,
+        f: F,
+    ) -> Self::Ref<U> {
+        R::map_ref(ref_, f)
+    }
 
-// impl<T> std::ops::Deref for MappedSignal<T> {
-//     type Target = dyn Fn() -> T;
+    fn try_map_ref<I: ?Sized, U: ?Sized, F: FnOnce(&I) -> Option<&U>>(
+        ref_: Self::Ref<I>,
+        f: F,
+    ) -> Option<Self::Ref<U>> {
+        R::try_map_ref(ref_, f)
+    }
 
-//     fn deref(&self) -> &Self::Target {
-//         // https://github.com/dtolnay/case-studies/tree/master/callable-types
+    fn try_read(&self) -> Result<Self::Ref<O>, generational_box::BorrowError> {
+        self.readable
+            .try_read()
+            .map(|ref_| R::map_ref(ref_, |r| (self.mapping)(r)))
+    }
 
-//         // First we create a closure that captures something with the Same in memory layout as Self (MaybeUninit<Self>).
-//         let uninit_callable = std::mem::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 || Self::read(unsafe { &*uninit_callable.as_ptr() });
+    fn peek(&self) -> Self::Ref<Self::Target> {
+        R::map_ref(self.readable.peek(), |r| (self.mapping)(r))
+    }
+}
 
-//         // 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>());
+impl<O, R> IntoAttributeValue for MappedSignal<O, R>
+where
+    O: Clone + IntoAttributeValue + ?Sized,
+    R: Readable + 'static,
+{
+    fn into_value(self) -> dioxus_core::AttributeValue {
+        self.with(|f| f.clone().into_value())
+    }
+}
 
-//         // 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) },
-//         );
+impl<O, R> PartialEq for MappedSignal<O, R>
+where
+    O: ?Sized,
+    R: PartialEq + Readable + 'static,
+{
+    fn eq(&self, other: &Self) -> bool {
+        self.readable == other.readable && std::ptr::eq(&self.mapping, &other.mapping)
+    }
+}
 
-//         // Cast the closure to a trait object.
-//         reference_to_closure as &Self::Target
-//     }
-// }
+/// Allow calling a signal with signal() syntax
+///
+/// Currently only limited to copy types, though could probably specialize for string/arc/rc
+impl<O, R> Deref for MappedSignal<O, R>
+where
+    O: Clone,
+    R: Readable + 'static,
+{
+    type Target = dyn Fn() -> O;
+
+    fn deref(&self) -> &Self::Target {
+        Readable::deref_impl(self)
+    }
+}

packages/signals/src/read.rs

@@ -3,13 +3,15 @@ use std::{
     ops::{Deref, Index},
 };
 
+use crate::MappedSignal;
+
 /// A trait for states that can be read from like [`crate::Signal`], [`crate::GlobalSignal`], or [`crate::ReadOnlySignal`]. You may choose to accept this trait as a parameter instead of the concrete type to allow for more flexibility in your API. For example, instead of creating two functions, one that accepts a [`crate::Signal`] and one that accepts a [`crate::GlobalSignal`], you can create one function that accepts a [`Readable`] type.
 pub trait Readable {
     /// The target type of the reference.
     type Target: ?Sized + 'static;
 
     /// The type of the reference.
-    type Ref<R: ?Sized + 'static>: Deref<Target = R>;
+    type Ref<R: ?Sized + 'static>: Deref<Target = R> + 'static;
 
     /// Map the reference to a new type.
     fn map_ref<I: ?Sized, U: ?Sized, F: FnOnce(&I) -> &U>(ref_: Self::Ref<I>, f: F)
@@ -24,6 +26,14 @@ pub trait Readable {
     /// Try to get the current value of the state. If this is a signal, this will subscribe the current scope to the signal. If the value has been dropped, this will panic.
     fn try_read(&self) -> Result<Self::Ref<Self::Target>, generational_box::BorrowError>;
 
+    /// Map the readable type to a new type.
+    fn map<O>(self, f: impl Fn(&Self::Target) -> &O + 'static) -> MappedSignal<O, Self>
+    where
+        Self: Sized + 'static,
+    {
+        MappedSignal::new(self, f)
+    }
+
     /// Get the current value of the state. If this is a signal, this will subscribe the current scope to the signal. If the value has been dropped, this will panic.
     #[track_caller]
     fn read(&self) -> Self::Ref<Self::Target> {
@@ -132,26 +142,24 @@ pub trait ReadableVecExt<T: 'static>: Readable<Target = Vec<T>> {
 
     /// Get an iterator over the values of the inner vector.
     #[track_caller]
-    fn iter(&self) -> ReadableValueIterator<'_, T, Self>
+    fn iter(&self) -> ReadableValueIterator<'_, Self>
     where
         Self: Sized,
     {
         ReadableValueIterator {
             index: 0,
             value: self,
-            phantom: std::marker::PhantomData,
         }
     }
 }
 
 /// An iterator over the values of a `Readable<Vec<T>>`.
-pub struct ReadableValueIterator<'a, T, R> {
+pub struct ReadableValueIterator<'a, R> {
     index: usize,
     value: &'a R,
-    phantom: std::marker::PhantomData<T>,
 }
 
-impl<'a, T: 'static, R: Readable<Target = Vec<T>>> Iterator for ReadableValueIterator<'a, T, R> {
+impl<'a, T: 'static, R: Readable<Target = Vec<T>>> Iterator for ReadableValueIterator<'a, R> {
     type Item = R::Ref<T>;
 
     fn next(&mut self) -> Option<Self::Item> {

packages/signals/src/signal.rs

@@ -1,6 +1,6 @@
 use crate::{
-    read::Readable, write::Writable, CopyValue, GlobalMemo, GlobalSignal, MappedSignal,
-    ReactiveContext, ReadOnlySignal,
+    read::Readable, write::Writable, CopyValue, GlobalMemo, GlobalSignal, ReactiveContext,
+    ReadOnlySignal,
 };
 use dioxus_core::{
     prelude::{flush_sync, spawn, IntoAttributeValue},
@@ -187,12 +187,6 @@ impl<T: 'static, S: Storage<SignalData<T>>> Signal<T, S> {
         }
     }
 
-    /// Map the signal to a new type.
-    pub fn map<O>(self, f: impl Fn(&T) -> &O + 'static) -> MappedSignal<S::Ref<O>> {
-        // MappedSignal::new(self, f)
-        todo!()
-    }
-
     /// Get the generational id of the signal.
     pub fn id(&self) -> generational_box::GenerationalBoxId {
         self.inner.id()

packages/signals/src/write.rs

@@ -6,7 +6,7 @@ use crate::read::Readable;
 /// A trait for states that can be read from like [`crate::Signal`], or [`crate::GlobalSignal`]. You may choose to accept this trait as a parameter instead of the concrete type to allow for more flexibility in your API. For example, instead of creating two functions, one that accepts a [`crate::Signal`] and one that accepts a [`crate::GlobalSignal`], you can create one function that accepts a [`Writable`] type.
 pub trait Writable: Readable {
     /// The type of the reference.
-    type Mut<R: ?Sized + 'static>: DerefMut<Target = R>;
+    type Mut<R: ?Sized + 'static>: DerefMut<Target = R> + 'static;
 
     /// Map the reference to a new type.
     fn map_mut<I: ?Sized, U: ?Sized, F: FnOnce(&mut I) -> &mut U>(
@@ -68,7 +68,7 @@ pub trait Writable: Readable {
     where
         Self::Target: Default,
     {
-        self.with_mut(|v| std::mem::take(v))
+        self.with_mut(std::mem::take)
     }
 
     /// Replace the value in the Signal, returning the old value.
@@ -184,26 +184,24 @@ pub trait WritableVecExt<T: 'static>: Writable<Target = Vec<T>> {
 
     /// Gets an iterator over the values of the vector.
     #[track_caller]
-    fn iter_mut(&self) -> WritableValueIterator<T, Self>
+    fn iter_mut(&self) -> WritableValueIterator<Self>
     where
         Self: Sized + Clone,
     {
         WritableValueIterator {
             index: 0,
             value: self.clone(),
-            phantom: std::marker::PhantomData,
         }
     }
 }
 
 /// An iterator over the values of a `Writable<Vec<T>>`.
-pub struct WritableValueIterator<T, R> {
+pub struct WritableValueIterator<R> {
     index: usize,
     value: R,
-    phantom: std::marker::PhantomData<T>,
 }
 
-impl<T: 'static, R: Writable<Target = Vec<T>>> Iterator for WritableValueIterator<T, R> {
+impl<T: 'static, R: Writable<Target = Vec<T>>> Iterator for WritableValueIterator<R> {
     type Item = R::Mut<T>;
 
     fn next(&mut self) -> Option<Self::Item> {