Callback constructor for FutureLink (#1272)

* initial implementation of #1271 callback constructor for FutureLink

* #1271 fix implementations to match function signature of trait

* #1271 fix failing build

yewtil/src/future.rs

@@ -8,14 +8,29 @@ use yew::{
 /// Trait that allows you to use `ComponentLink` and `AgentLink` to register futures.
 pub trait LinkFuture {
     type Message;
+
+    /// This method creates a `Callback` which returns a Future which
+    /// returns a message to be sent back to the component's event
+    /// loop.
+    ///
+    /// # Panics
+    /// If the future panics, then the promise will not resolve, and
+    /// will leak.
+    fn callback_future<FN, FU, IN, M>(&self, function: FN) -> yew::Callback<IN>
+    where
+        M: Into<Self::Message>,
+        FU: Future<Output = M> + 'static,
+        FN: Fn(IN) -> FU + 'static;
+
     /// This method processes a Future that returns a message and sends it back to the component's
     /// loop.
     ///
     /// # Panics
     /// If the future panics, then the promise will not resolve, and will leak.
-    fn send_future<F>(&self, future: F)
+    fn send_future<F, M>(&self, future: F)
     where
-        F: Future<Output = Self::Message> + 'static;
+        M: Into<Self::Message>,
+        F: Future<Output = M> + 'static;
 
     /// Registers a future that resolves to multiple messages.
     /// # Panics
@@ -28,13 +43,30 @@ pub trait LinkFuture {
 impl<COMP: Component> LinkFuture for ComponentLink<COMP> {
     type Message = COMP::Message;
 
-    fn send_future<F>(&self, future: F)
+    fn callback_future<FN, FU, IN, M>(&self, function: FN) -> yew::Callback<IN>
     where
-        F: Future<Output = Self::Message> + 'static,
+        M: Into<Self::Message>,
+        FU: Future<Output = M> + 'static,
+        FN: Fn(IN) -> FU + 'static,
+    {
+        let link = self.clone();
+
+        let closure = move |input: IN| {
+            let future: FU = function(input);
+            link.send_future(future);
+        };
+
+        closure.into()
+    }
+
+    fn send_future<F, M>(&self, future: F)
+    where
+        M: Into<Self::Message>,
+        F: Future<Output = M> + 'static,
     {
         let link: ComponentLink<COMP> = self.clone();
         let js_future = async move {
-            let message: COMP::Message = future.await;
+            let message: COMP::Message = future.await.into();
             link.send_message(message);
         };
         spawn_local(js_future);
@@ -56,13 +88,30 @@ impl<COMP: Component> LinkFuture for ComponentLink<COMP> {
 impl<AGN: Agent> LinkFuture for AgentLink<AGN> {
     type Message = AGN::Message;
 
-    fn send_future<F>(&self, future: F)
+    fn callback_future<FN, FU, IN, M>(&self, function: FN) -> yew::Callback<IN>
     where
-        F: Future<Output = Self::Message> + 'static,
+        M: Into<Self::Message>,
+        FU: Future<Output = M> + 'static,
+        FN: Fn(IN) -> FU + 'static,
+    {
+        let link = self.clone();
+
+        let closure = move |input: IN| {
+            let future: FU = function(input);
+            link.send_future(future);
+        };
+
+        closure.into()
+    }
+
+    fn send_future<F, M>(&self, future: F)
+    where
+        M: Into<Self::Message>,
+        F: Future<Output = M> + 'static,
     {
         let link: AgentLink<AGN> = self.clone();
         let js_future = async move {
-            let message: AGN::Message = future.await;
+            let message: AGN::Message = future.await.into();
             let cb = link.callback(|m: AGN::Message| m);
             cb.emit(message);
         };