support functors

hdr/sqlite_modern_cpp/utility/function_traits.h

@@ -31,5 +31,26 @@ namespace sqlite {
 			static const std::size_t arity = sizeof...(Arguments);
 		};
 
+    /* support the non-const operator ()
+     * this will work with user defined functors */
+		template <
+			typename    ClassType,
+			typename    ReturnType,
+			typename... Arguments
+		>
+		struct function_traits<
+			ReturnType(ClassType::*)(Arguments...)
+		> {
+			typedef ReturnType result_type;
+
+			template <std::size_t Index>
+			using argument = typename std::tuple_element<
+				Index,
+				std::tuple<Arguments...>
+			>::type;
+
+			static const std::size_t arity = sizeof...(Arguments);
+		};
+
 	}
 }

tests/functors.cc

@@ -0,0 +1,57 @@
+#include <iostream>
+#include <vector>
+#include <algorithm>
+#include <string>
+#include <sqlite_modern_cpp.h>
+
+using namespace sqlite;
+using namespace std;
+
+struct tbl_functor {
+  explicit tbl_functor(vector<pair<int, string> > &vec_) : vec(vec_) { }
+
+  void operator() ( int id, string name) {
+    vec.push_back(make_pair(id, move(name)));
+  }
+  vector<pair<int,string> > &vec;
+};
+
+int main() {
+
+  try {
+    database db(":memory:");
+    db << "CREATE TABLE tbl (id integer, name string);";
+    db << "INSERT INTO tbl VALUES (?, ?);" << 1 << "hello";
+    db << "INSERT INTO tbl VALUES (?, ?);" << 2 << "world";
+
+    vector<pair<int,string> > vec;
+    db << "select id,name from tbl;" >> tbl_functor(vec);
+
+    if(vec.size() != 2) {
+      cout << "Bad result on line " << __LINE__ << endl;
+      exit(EXIT_FAILURE);
+    }
+
+    vec.clear();
+
+    tbl_functor functor(vec);
+    db << "select id,name from tbl;" >> functor;
+
+    if(vec.size() != 2 || vec[0].first != 1 || vec[0].second != "hello") {
+      cout << "Bad result on line " << __LINE__ << endl;
+      exit(EXIT_FAILURE);
+    }
+
+  }
+  catch(sqlite_exception e) {
+    cout << "Unexpected error " << e.what() << endl;
+    exit(EXIT_FAILURE);
+  }
+  catch(...) {
+    cout << "Unknown error\n";
+    exit(EXIT_FAILURE);
+  }
+
+  cout << "OK\n";
+  exit(EXIT_SUCCESS);
+}