Implement time::repeat and simplify Subscription::run_with

futures/src/backend/native/tokio.rs

@@ -22,40 +22,25 @@ impl crate::Executor for Executor {
 
 pub mod time {
     //! Listen and react to time.
-    use crate::subscription::{self, Hasher, Subscription};
+    use crate::core::time::{Duration, Instant};
+    use crate::stream;
+    use crate::subscription::Subscription;
+    use crate::MaybeSend;
+
+    use futures::SinkExt;
+    use std::future::Future;
 
     /// Returns a [`Subscription`] that produces messages at a set interval.
     ///
     /// The first message is produced after a `duration`, and then continues to
     /// produce more messages every `duration` after that.
-    pub fn every(
+    pub fn every(duration: Duration) -> Subscription<Instant> {
-        duration: std::time::Duration,
+        Subscription::run_with(duration, |duration| {
-    ) -> Subscription<std::time::Instant> {
-        subscription::from_recipe(Every(duration))
-    }
-
-    #[derive(Debug)]
-    struct Every(std::time::Duration);
-
-    impl subscription::Recipe for Every {
-        type Output = std::time::Instant;
-
-        fn hash(&self, state: &mut Hasher) {
-            use std::hash::Hash;
-
-            std::any::TypeId::of::<Self>().hash(state);
-            self.0.hash(state);
-        }
-
-        fn stream(
-            self: Box<Self>,
-            _input: subscription::EventStream,
-        ) -> futures::stream::BoxStream<'static, Self::Output> {
             use futures::stream::StreamExt;
 
-            let start = tokio::time::Instant::now() + self.0;
+            let start = tokio::time::Instant::now() + *duration;
 
-            let mut interval = tokio::time::interval_at(start, self.0);
+            let mut interval = tokio::time::interval_at(start, *duration);
             interval.set_missed_tick_behavior(
                 tokio::time::MissedTickBehavior::Skip,
             );
@@ -67,6 +52,27 @@ pub mod time {
             };
 
             stream.map(tokio::time::Instant::into_std).boxed()
-        }
+        })
+    }
+
+    /// Returns a [`Subscription`] that runs the given async function at a
+    /// set interval; producing the result of the function as output.
+    pub fn repeat<F, T>(f: fn() -> F, interval: Duration) -> Subscription<T>
+    where
+        F: Future<Output = T> + MaybeSend + 'static,
+        T: MaybeSend + 'static,
+    {
+        Subscription::run_with((f, interval), |(f, interval)| {
+            let f = *f;
+            let interval = *interval;
+
+            stream::channel(1, move |mut output| async move {
+                loop {
+                    let _ = output.send(f().await).await;
+
+                    tokio::time::sleep(interval).await;
+                }
+            })
+        })
     }
 }

futures/src/subscription.rs

@@ -202,8 +202,8 @@ impl<T> Subscription<T> {
         T: 'static,
     {
         from_recipe(Runner {
-            id: builder,
+            data: builder,
-            spawn: move |_| builder(),
+            spawn: |builder, _| builder(),
         })
     }
 
@@ -211,15 +211,15 @@ impl<T> Subscription<T> {
     /// given [`Stream`].
     ///
     /// The `id` will be used to uniquely identify the [`Subscription`].
-    pub fn run_with_id<I, S>(id: I, stream: S) -> Subscription<T>
+    pub fn run_with<D, S>(data: D, builder: fn(&D) -> S) -> Self
     where
-        I: Hash + 'static,
+        D: Hash + 'static,
         S: Stream<Item = T> + MaybeSend + 'static,
         T: 'static,
     {
         from_recipe(Runner {
-            id,
+            data: (data, builder),
-            spawn: move |_| stream,
+            spawn: |(data, builder), _| builder(data),
         })
     }
 
@@ -423,8 +423,8 @@ where
     T: 'static + MaybeSend,
 {
     from_recipe(Runner {
-        id,
+        data: id,
-        spawn: |events| {
+        spawn: |_, events| {
             use futures::future;
             use futures::stream::StreamExt;
 
@@ -435,27 +435,27 @@ where
 
 struct Runner<I, F, S, T>
 where
-    F: FnOnce(EventStream) -> S,
+    F: FnOnce(&I, EventStream) -> S,
     S: Stream<Item = T>,
 {
-    id: I,
+    data: I,
     spawn: F,
 }
 
 impl<I, F, S, T> Recipe for Runner<I, F, S, T>
 where
     I: Hash + 'static,
-    F: FnOnce(EventStream) -> S,
+    F: FnOnce(&I, EventStream) -> S,
     S: Stream<Item = T> + MaybeSend + 'static,
 {
     type Output = T;
 
     fn hash(&self, state: &mut Hasher) {
         std::any::TypeId::of::<I>().hash(state);
-        self.id.hash(state);
+        self.data.hash(state);
     }
 
     fn stream(self: Box<Self>, input: EventStream) -> BoxStream<Self::Output> {
-        crate::boxed_stream((self.spawn)(input))
+        crate::boxed_stream((self.spawn)(&self.data, input))
     }
 }

src/lib.rs

@@ -365,9 +365,9 @@
 //!
 //! As with tasks, some modules expose convenient functions that build a [`Subscription`] for you—like
 //! [`time::every`] which can be used to listen to time, or [`keyboard::on_key_press`] which will notify you
-//! of any key presses. But you can also create your own with [`Subscription::run`] and [`run_with_id`].
+//! of any key presses. But you can also create your own with [`Subscription::run`] and [`run_with`].
 //!
-//! [`run_with_id`]: Subscription::run_with_id
+//! [`run_with`]: Subscription::run_with
 //!
 //! ## Scaling Applications
 //! The `update`, `view`, and `Message` triplet composes very nicely.