3 files changed, 22 insertions, 7 deletions
diff --git a/src/openvic-simulation/types/HasIdentifier.hpp b/src/openvic-simulation/types/HasIdentifier.hpp
index 925d58b..74961e3 100644
--- a/src/openvic-simulation/types/HasIdentifier.hpp
+++ b/src/openvic-simulation/types/HasIdentifier.hpp
@@ -2,6 +2,8 @@
 
 #include <algorithm>
 #include <cassert>
+#include <string>
+#include <string_view>
 #include <ostream>
 
 #include "openvic-simulation/types/Colour.hpp"
@@ -49,6 +51,11 @@ namespace OpenVic {
 		return obj != nullptr ? stream << *obj : stream << "<NULL>";
 	}
 
+	template<typename T>
+	concept HasGetIdentifier = requires(T const& t) {
+		{ t.get_identifier() } -> std::same_as<std::string_view>;
+	};
+
 	/*
 	 * Base class for objects with associated colour information.
 	 */
@@ -71,6 +78,11 @@ namespace OpenVic {
 	using HasColour = _HasColour<colour_t>;
 	using HasAlphaColour = _HasColour<colour_argb_t>;
 
+	template<typename T>
+	concept HasGetColour = requires(T const& t) {
+		{ t.get_colour() } -> IsColour;
+	};
+
 	/*
 	 * Base class for objects with a unique string identifier and associated colour information.
 	 */
@@ -107,4 +119,9 @@ namespace OpenVic {
 		HasIndex& operator=(HasIndex const&) = delete;
 		HasIndex& operator=(HasIndex&&) = delete;
 	};
+
+	template<typename T>
+	concept HasGetIndex = requires(T const& t) {
+		{ t.get_index() } -> std::unsigned_integral;
+	};
 }
diff --git a/src/openvic-simulation/types/IdentifierRegistry.hpp b/src/openvic-simulation/types/IdentifierRegistry.hpp
index a73ebcc..03cdbb1 100644
--- a/src/openvic-simulation/types/IdentifierRegistry.hpp
+++ b/src/openvic-simulation/types/IdentifierRegistry.hpp
@@ -4,6 +4,7 @@
 
 #include "openvic-simulation/dataloader/NodeTools.hpp"
 #include "openvic-simulation/types/fixed_point/FixedPointMap.hpp"
+#include "openvic-simulation/types/HasIdentifier.hpp"
 #include "openvic-simulation/utility/Getters.hpp"
 #include "openvic-simulation/utility/Logger.hpp"
 
@@ -27,11 +28,6 @@ namespace OpenVic {
 		return true;
 	}
 
-	template<typename T>
-	concept HasGetIdentifier = requires(T const& t) {
-		{ t.get_identifier() } -> std::same_as<std::string_view>;
-	};
-
 	/* Registry Value Info - the type that is being registered, and a unique identifier string getter. */
 	template<typename ValueInfo>
 	concept RegistryValueInfo = requires(
diff --git a/src/openvic-simulation/types/IndexedMap.hpp b/src/openvic-simulation/types/IndexedMap.hpp
index 68effb9..30cf5cd 100644
--- a/src/openvic-simulation/types/IndexedMap.hpp
+++ b/src/openvic-simulation/types/IndexedMap.hpp
@@ -14,6 +14,8 @@ namespace OpenVic {
 		using container_t = std::vector<Value>;
 		using key_t = Key;
 		using value_t = Value;
+		using value_ref_t = container_t::reference;
+		using value_const_ref_t = container_t::const_reference;
 		using keys_t = std::vector<key_t>;
 
 		using container_t::operator[];
@@ -91,11 +93,11 @@ namespace OpenVic {
 			}
 		}
 
-		constexpr value_t& operator[](key_t const& key) {
+		constexpr value_ref_t operator[](key_t const& key) {
 			return container_t::operator[](get_index_from_item(key));
 		}
 
-		constexpr value_t const& operator[](key_t const& key) const {
+		constexpr value_const_ref_t operator[](key_t const& key) const {
 			return container_t::operator[](get_index_from_item(key));
 		}