Add a method to fetch an unhashed key, close paritytech#100 (parityte…

…ch#152)

* Add a method to fetch an unhashed key, close paritytech#100

* Return decoded value

* Refactoring

src/lib.rs

@@ -258,20 +258,29 @@ impl<T: Runtime> Client<T> {
  &self.metadata
  }
 
- /// Fetch a StorageKey with an optional block hash.
- pub async fn fetch<F: Store<T>>(
+ /// Fetch the value under an unhashed storage key
+ pub async fn fetch_unhashed<V: Decode>(
  &self,
- store: &F,
+ key: StorageKey,
  hash: Option<T::Hash>,
- ) -> Result<Option<F::Returns>, Error> {
- let key = store.key(&self.metadata)?;
+ ) -> Result<Option<V>, Error> {
  if let Some(data) = self.rpc.storage(&key, hash).await? {
  Ok(Some(Decode::decode(&mut &data.0[..])?))
  } else {
  Ok(None)
  }
  }
 
+ /// Fetch a StorageKey with an optional block hash.
+ pub async fn fetch<F: Store<T>>(
+ &self,
+ store: &F,
+ hash: Option<T::Hash>,
+ ) -> Result<Option<F::Returns>, Error> {
+ let key = store.key(&self.metadata)?;
+ self.fetch_unhashed::<F::Returns>(key, hash).await
+ }
+
  /// Fetch a StorageKey that has a default value with an optional block hash.
  pub async fn fetch_or_default<F: Store<T>>(
  &self,