add setting key value in struct for ForEach queries

foreach_test.go

@@ -87,3 +87,61 @@ func TestForEachInBucket(t *testing.T) {
 		}
 	})
 }
+
+func TestForEachKeyStructTag(t *testing.T) {
+	testWrap(t, func(store *bolthold.Store, t *testing.T) {
+		type KeyTest struct {
+			Key   int `boltholdKey:"Key"`
+			Value string
+		}
+
+		key := 3
+
+		err := store.Insert(key, &KeyTest{
+			Value: "test value",
+		})
+
+		if err != nil {
+			t.Fatalf("Error inserting KeyTest struct for Key struct tag testing. Error: %s", err)
+		}
+
+		err = store.ForEach(bolthold.Where(bolthold.Key).Eq(key), func(result *KeyTest) error {
+			if result.Key != key {
+				t.Fatalf("Key struct tag was not set correctly.  Expected %d, got %d", key, result.Key)
+			}
+			return nil
+		})
+		if err != nil {
+			t.Fatalf("Error running ForEach in TestKeyStructTag. ERROR: %s", err)
+		}
+	})
+}
+
+func TestForEachKeyStructTagIntoPtr(t *testing.T) {
+	testWrap(t, func(store *bolthold.Store, t *testing.T) {
+		type KeyTest struct {
+			Key   *int `boltholdKey:"Key"`
+			Value string
+		}
+
+		key := 3
+
+		err := store.Insert(&key, &KeyTest{
+			Value: "test value",
+		})
+
+		if err != nil {
+			t.Fatalf("Error inserting KeyTest struct for Key struct tag testing. Error: %s", err)
+		}
+
+		err = store.ForEach(bolthold.Where(bolthold.Key).Eq(key), func(result *KeyTest) error {
+			if result.Key == nil || *result.Key != key {
+				t.Fatalf("Key struct tag was not set correctly.  Expected %d, got %d", key, result.Key)
+			}
+			return nil
+		})
+		if err != nil {
+			t.Fatalf("Error running ForEach in TestKeyStructTag. ERROR: %s", err)
+		}
+	})
+}

query.go

@@ -562,7 +562,29 @@ func (s *Store) forEach(source BucketSource, query *Query, fn interface{}) error
 
 	dataType := reflect.New(argType).Interface()
 
+	var keyType reflect.Type
+	var keyField string
+
+	for i := 0; i < argType.NumField(); i++ {
+		if strings.Contains(string(argType.Field(i).Tag), BoltholdKeyTag) {
+			keyType = argType.Field(i).Type
+			keyField = argType.Field(i).Name
+			break
+		}
+	}
+
 	return s.runQuery(source, dataType, query, nil, query.skip, func(r *record) error {
+		if keyType != nil {
+			rowKey := r.value
+			for rowKey.Kind() == reflect.Ptr {
+				rowKey = rowKey.Elem()
+			}
+			err := s.decode(r.key, rowKey.FieldByName(keyField).Addr().Interface())
+			if err != nil {
+				return err
+			}
+		}
+
 		out := fnVal.Call([]reflect.Value{r.value})
 		if len(out) != 1 {
 			return fmt.Errorf("foreach function does not return an error")