Perform a code refactoring: create a universal helper for checking the existence of entities and fix the identified issues.

For refactoring entity existence checks, you can create a universal template function that takes an identifier and a search function, returning a boolean value. This reduces duplication and improves readability.

Example in C++:

#include <optional>
#include <functional>

// Universal helper for checking entity existence
template<typename IdType, typename EntityType>
bool entityExists(const IdType& id, const std::function<std::optional<EntityType>(const IdType&)>& finder) {
    return finder(id).has_value();
}

// Usage example:
// std::optional<User> findUserById(const int& id);
// bool exists = entityExists<int, User>(userId, findUserById);

Identified issues are usually related to code duplication and lack of error handling. It is also important to ensure that search functions correctly return an empty optional when the entity is absent to avoid undefined behavior.