smartcontractkit · apopiak · Mar 29, 2021
diff --git a/pallet-chainlink-feed/src/lib.rs b/pallet-chainlink-feed/src/lib.rs
@@ -66,6 +66,8 @@ pub trait Trait: frame_system::Trait {
 	/// Number of rounds to keep around per feed.
 	type PruningWindow: Get<RoundId>;
 
+	type OnAnswerHandler: OnAnswerHandler<Self>;
+
 	/// The weight for this pallet's extrinsics.
 	type WeightInfo: WeightInfo;
 }
@@ -208,6 +210,16 @@ impl<B, V> TryFrom<Round<B, V>> for RoundData<B, V> {
 	}
 }
 
+pub trait OnAnswerHandler<T: Trait> {
+	fn on_answer(feed: T::FeedId, new_data: RoundData<T::BlockNumber, T::Value>);
+}
+
+impl<T: Trait> OnAnswerHandler<T> for () {
+	fn on_answer(_feed: T::FeedId, _new_data: RoundData<T::BlockNumber, T::Value>) {
+		// noop
+	}
+}
+
 /// Trait for interacting with the feeds in the pallet.
 pub trait FeedOracle {
 	type FeedId: Parameter + BaseArithmetic;
@@ -596,6 +608,7 @@ decl_module! {
 					let updated_at = frame_system::Module::<T>::block_number();
 					round.updated_at = Some(updated_at);
 					round.answered_in_round = Some(round_id);
+					let round_data = round.clone().try_into().expect("round does not have empty fields and will therefore convert; qed");
 					Rounds::<T>::insert(feed_id, round_id, round);
 
 					feed.config.latest_round = round_id;
@@ -608,8 +621,11 @@ decl_module! {
 						Details::<T>::remove(feed_id, prev_round_id);
 					}
 
+					T::OnAnswerHandler::on_answer(feed_id, round_data);
+
 					Self::deposit_event(RawEvent::AnswerUpdated(
 						feed_id, round_id, new_answer, updated_at));
+
 				}
 
 				// update oracle rewards and try to reserve them

diff --git a/substrate-node-example/pallets/template/src/lib.rs b/substrate-node-example/pallets/template/src/lib.rs
@@ -7,7 +7,7 @@
 use frame_support::{decl_module, decl_storage, decl_event, decl_error, dispatch, traits::Get};
 use frame_system::ensure_signed;
 
-use pallet_chainlink_feed::{FeedInterface, FeedOracle, RoundData};
+use pallet_chainlink_feed::{FeedInterface, FeedOracle, OnAnswerHandler, RoundData, Trait as FeedTrait};
 
 #[cfg(test)]
 mod mock;
@@ -43,11 +43,13 @@ decl_event!(
 	where
 		AccountId = <T as frame_system::Trait>::AccountId,
 		Value = <<<T as Trait>::Oracle as FeedOracle>::Feed as FeedInterface>::Value,
+		FeedValue = <T as FeedTrait>::Value,
 	{
 		/// Event documentation should end with an array that provides descriptive names for event
 		/// parameters. [something, who]
 		SomethingStored(u32, AccountId),
 		NewData(Value),
+		NewFeedValue(FeedValue),
 	}
 );
 
@@ -122,3 +124,11 @@ decl_module! {
 		}
 	}
 }
+
+impl<T: Trait + FeedTrait> OnAnswerHandler<T> for Module<T> {
+	fn on_answer(feed: <T as FeedTrait>::FeedId, round_data: RoundData<T::BlockNumber, <T as FeedTrait>::Value>) {
+		let RoundData { answer, .. } = round_data;
+		frame_support::debug::info!("feed: {:?}, new data: {:?}", feed, answer);
+		Self::deposit_event(RawEvent::NewData(answer));
+	}
+}
diff --git a/substrate-node-example/runtime/src/lib.rs b/substrate-node-example/runtime/src/lib.rs
@@ -289,6 +289,7 @@ impl pallet_chainlink_feed::Trait for Runtime {
 	type OracleCountLimit = OracleCountLimit;
 	type FeedLimit = FeedLimit;
 	type PruningWindow = PruningWindow;
+	type OnAnswerHandler = TemplateModule;
 	type WeightInfo = ChainlinkWeightInfo;
 }