Core/Util: Added another template utility - find_type_if

* Trinity::find_type_if - Find a type matching predicate in a given template parameter pack

1 files changed, 68 insertions, 0 deletions

diff --git a/src/common/Utilities/Types.h b/src/common/Utilities/Types.h
new file mode 100644
index 00000000000..ab78fb871a9
--- /dev/null
+++ b/src/common/Utilities/Types.h
@@ -0,0 +1,68 @@
+/*
+ * This file is part of the TrinityCore Project. See AUTHORS file for Copyright information
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef Types_h__
+#define Types_h__
+
+#include "advstd.h"
+
+namespace Trinity
+{
+    // end "iterator" tag for find_type_if
+    struct find_type_end;
+
+    template<template<typename...> typename Check, typename... Ts>
+    struct find_type_if;
+
+    template<template<typename...> typename Check>
+    struct find_type_if<Check>
+    {
+        using type = find_type_end;
+    };
+
+    template<template<typename...> typename Check, typename T1, typename... Ts>
+    struct find_type_if<Check, T1, Ts...> : std::conditional_t<Check<T1>::value, advstd::type_identity<T1>, find_type_if<Check, Ts...>>
+    {
+    };
+
+    /*
+        Utility to find a type matching predicate (Check) in a given type list (Ts)
+        Evaluates to first type matching predicate or find_type_end
+        Check must be a type that contains static bool ::value, _v aliases don't work
+
+        template<typename... Ts>
+        struct Example
+        {
+            using TupleArg = Trinity::find_type_if_t<Trinity::is_tuple, Ts...>;
+
+            bool HasTuple()
+            {
+                return !std::is_same_v<TupleArg, Trinity::find_type_end>;
+            }
+        };
+
+        Example<int, std::string, std::tuple<int, int, int>, char> example;
+        example.HasTuple() == true; // TupleArg is std::tuple<int, int, int>
+
+        Example<int, std::string, char> example2;
+        example2.HasTuple() == false; // TupleArg is Trinity::find_type_end
+    */
+    template<template<typename...> typename Check, typename... Ts>
+    using find_type_if_t = typename find_type_if<Check, Ts...>::type;
+}
+
+#endif // Types_h__