Merge pull request #19 from contour-terminal/improvement/collectdifference_with_ind

collectDifferences with first argument beeing index of the data member

Author: Yaraslaut

include/reflection-cpp/reflection.hpp

@@ -812,6 +812,25 @@ void CollectDifferences(const Object& lhs, const Object& rhs, Callback&& callbac
     });
 }
 
+template <typename Object, typename Callback>
+requires std::same_as<void, std::invoke_result_t<Callback, size_t, MemberTypeOf<0, Object>, MemberTypeOf<0, Object>>>
+void CollectDifferences(const Object& lhs, const Object& rhs, Callback&& callback)
+{
+    template_for<0, CountMembers<Object>>([&]<auto I>() {
+        if constexpr (std::equality_comparable<MemberTypeOf<I, Object>>)
+        {
+            if (GetMemberAt<I>(lhs) != GetMemberAt<I>(rhs))
+            {
+                callback(I, GetMemberAt<I>(lhs), GetMemberAt<I>(rhs));
+            }
+        }
+        else
+        {
+            CollectDifferences(GetMemberAt<I>(lhs), GetMemberAt<I>(rhs), callback);
+        }
+    });
+}
+
 } // namespace Reflection
 
 template <std::size_t N>

test-reflection-cpp.cpp

@@ -203,6 +203,23 @@ TEST_CASE("Compare.simple", "[reflection]")
     CHECK(diff == "id: 1 != 2\nname: John Doe != Jane Doe\nage: 42 != 43\n");
 }
 
+
+
+TEST_CASE("Compare.simple_with_indexing", "[reflection]")
+{
+    auto const r1 = Record { .id = 1, .name = "John Doe", .age = 42 };
+    auto const r2 = Record { .id = 2, .name = "John Doe", .age = 42 };
+
+    size_t check = -1;
+    auto differenceCallback = [&](size_t ind, auto const& lhs, auto const& rhs) {
+        check = ind;
+    };
+
+    Reflection::CollectDifferences(r1, r2, differenceCallback);
+    CHECK(check == 0);
+}
+
+
 struct Table
 {
     Record first;