add snapshotAtIndex to indexed data sources

FirebaseDatabaseUI/FUIIndexArray.h

@@ -33,7 +33,7 @@ NS_ASSUME_NONNULL_BEGIN
 @optional
 
 /**
- * Delegate method called when the database reference at an index has 
+ * Delegate method called when the database reference at an index has
  * finished loading its contents.
  * @param array The array containing the reference.
  * @param ref The reference that was loaded.

FirebaseDatabaseUI/FUIIndexCollectionViewDataSource.h

@@ -91,6 +91,14 @@ didFailLoadAtIndex:(NSUInteger)index
                                                          NSIndexPath *indexPath,
                                                          FIRDataSnapshot *_Nullable snap))populateCell NS_DESIGNATED_INITIALIZER;
 
+/**
+ * Returns the snapshot at the given index, if it has loaded.
+ * Raises a fatal error if the index is out of bounds.
+ * @param index The index of the requested snapshot.
+ * @return A snapshot, or nil if one has not yet been loaded.
+ */
+- (nullable FIRDataSnapshot *)snapshotAtIndex:(NSInteger)index;
+
 @end
 
 @interface UICollectionView (FUIIndexCollectionViewDataSource)

FirebaseDatabaseUI/FUIIndexCollectionViewDataSource.m

@@ -54,6 +54,10 @@ - (instancetype)initWithIndex:(FIRDatabaseQuery *)indexQuery
   return self.array.indexes;
 }
 
+- (FIRDataSnapshot *)snapshotAtIndex:(NSInteger)index {
+  return [self.array objectAtIndex:index];
+}
+
 #pragma mark - FUIIndexArrayDelegate
 
 - (void)array:(FUIIndexArray *)array

FirebaseDatabaseUI/FUIIndexTableViewDataSource.h

@@ -91,6 +91,14 @@ didFailLoadAtIndex:(NSUInteger)index
                                                     NSIndexPath *indexPath,
                                                     FIRDataSnapshot *_Nullable snap))populateCell NS_DESIGNATED_INITIALIZER;
 
+/**
+ * Returns the snapshot at the given index, if it has loaded.
+ * Raises a fatal error if the index is out of bounds.
+ * @param index The index of the requested snapshot.
+ * @return A snapshot, or nil if one has not yet been loaded.
+ */
+- (nullable FIRDataSnapshot *)snapshotAtIndex:(NSInteger)index;
+
 @end
 
 @interface UITableView (FUIIndexTableViewDataSource)

FirebaseDatabaseUI/FUIIndexTableViewDataSource.m

@@ -62,6 +62,10 @@ - (instancetype)initWithIndex:(FIRDatabaseQuery *)indexQuery
   return self.array.indexes;
 }
 
+- (FIRDataSnapshot *)snapshotAtIndex:(NSInteger)index {
+  return [self.array objectAtIndex:index];
+}
+
 #pragma mark - FUIIndexArrayDelegate 
 
 - (void)array:(FUIIndexArray *)array

FirebaseDatabaseUITests/FUIIndexCollectionViewDataSourceTest.m

@@ -183,4 +183,10 @@ - (void)testItUpdatesOnMove {
   XCTAssertEqualObjects(cell.accessibilityValue, @"3");
 }
 
+- (void)testItReturnsSnapshotsFromItsIndexArray {
+  FIRDataSnapshot *snap = [self.dataSource snapshotAtIndex:0];
+  XCTAssertEqualObjects(snap.key, @"data", @"expected snap's key to equal 'data', got %@ instead", snap.key);
+  XCTAssertEqualObjects(snap.value, @"1", @"expected snap's key to equal '1', got %@ instead", snap.value);
+}
+
 @end

FirebaseDatabaseUITests/FUIIndexTableViewDataSourceTest.m

@@ -178,4 +178,10 @@ - (void)testItUpdatesOnMove {
   XCTAssertEqualObjects(cell.accessibilityValue, @"3");
 }
 
+- (void)testItReturnsSnapshotsFromItsIndexArray {
+  FIRDataSnapshot *snap = [self.dataSource snapshotAtIndex:0];
+  XCTAssertEqualObjects(snap.key, @"data", @"expected snap's key to equal 'data', got %@ instead", snap.key);
+  XCTAssertEqualObjects(snap.value, @"1", @"expected snap's key to equal '1', got %@ instead", snap.value);
+}
+
 @end