Deduplicate the Store downcasting with a template

1 files changed, 16 insertions, 0 deletions

diff --git a/src/libstore/store-cast.hh b/src/libstore/store-cast.hh
new file mode 100644
index 000000000..ff62fc359
--- /dev/null
+++ b/src/libstore/store-cast.hh
@@ -0,0 +1,16 @@
+#pragma once
+
+#include "store-api.hh"
+
+namespace nix {
+
+template<typename T>
+T & require(Store & store)
+{
+    auto * castedStore = dynamic_cast<T *>(&store);
+    if (!castedStore)
+        throw UsageError("%s not supported by store '%s'", T::operationName, store.getUri());
+    return *castedStore;
+}
+
+}