From 955c48eca375ae3c62f5049e8ab8574e6c0cb6a1 Mon Sep 17 00:00:00 2001
From: NathanW <nathansward@comcast.net>
Date: Tue, 18 May 2021 16:27:45 -0600
Subject: [PATCH] implement Events::extend using impl std::iter::Extend

---
 crates/bevy_ecs/src/event.rs | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/crates/bevy_ecs/src/event.rs b/crates/bevy_ecs/src/event.rs
index 8f88fe8f3c82d5..9cf9c320138872 100644
--- a/crates/bevy_ecs/src/event.rs
+++ b/crates/bevy_ecs/src/event.rs
@@ -351,12 +351,27 @@ impl<T: Component> Events<T> {
         }
     }
 
-    pub fn extend<I>(&mut self, events: I)
+    /// Iterates over events that happened since the last "update" call.
+    /// WARNING: You probably don't want to use this call. In most cases you should use an
+    /// `EventReader`. You should only use this if you know you only need to consume events
+    /// between the last `update()` call and your call to `iter_current_update_events`.
+    /// If events happen outside that window, they will not be handled. For example, any events that
+    /// happen after this call and before the next `update()` call will be dropped.
+    pub fn iter_current_update_events(&self) -> impl DoubleEndedIterator<Item = &T> {
+        match self.state {
+            State::A => self.events_a.iter().map(map_instance_event),
+            State::B => self.events_b.iter().map(map_instance_event),
+        }
+    }
+}
+
+impl<T> std::iter::Extend<T> for Events<T> {
+    fn extend<I>(&mut self, iter: I)
     where
-        I: Iterator<Item = T>,
+        I: IntoIterator<Item = T>,
     {
         let mut event_count = self.event_count;
-        let events = events.map(|event| {
+        let events = iter.into_iter().map(|event| {
             let event_id = EventId {
                 id: event_count,
                 _marker: PhantomData,
@@ -496,4 +511,15 @@ mod tests {
     ) -> Vec<TestEvent> {
         reader.iter(events).cloned().collect::<Vec<TestEvent>>()
     }
+
+    #[test]
+    fn test_events_extent_impl() {
+        let mut events = Events::<TestEvent>::default();
+        let mut reader = events.get_reader();
+
+        events.extend(vec![TestEvent { i: 0 }, TestEvent { i: 1 }]);
+        assert!(reader
+            .iter(&events)
+            .eq([TestEvent { i: 0 }, TestEvent { i: 1 }].iter()));
+    }
 }