lix/src/libstore/store-cast.hh
John Ericson f4ab297b31 Ensure all headers have #pragma once and are in API docs
`///@file` makes them show up in the internal API dos. A tiny few were
missing `#pragma once`.
2023-03-31 23:19:44 -04:00

25 lines
554 B
C++

#pragma once
///@file
#include "store-api.hh"
namespace nix {
/**
* Helper to try downcasting a Store with a nice method if it fails.
*
* This is basically an alternative to the user-facing part of
* Store::unsupported that allows us to still have a nice message but
* better interface design.
*/
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;
}
}