second version

Author: aminroosta

README.md

@@ -9,62 +9,57 @@ This library is lightweight wrapper around sqlite C api .
 using namespace  sqlite;
 using namespace std;
 
+
 int main(){
 	try {
 		// creates a database file 'dbfile.db' if not exists
 		database db("dbfile.db");
 
-		// executes the query and creates a 'user' table
+		// executes the query and creates a 'user' table if not exists 
 		db <<
-			"create table user ("
+			"create table if not exists user ("
 			"	age int,"
 			"	name text,"
 			"	weight real"
 			");";
 
 		// inserts a new user and binds the values to ?
-		// note that only types allowed for bindings are 
-		//		1 - numeric types( int ,long ,long long, float, double , ... )
-		//		2 - string , wstring
+		// note that only types allowed for bindings are :
+		//		int ,long, long long, float, double 
+		//		string , wstring
 		db << "insert into user (age,name,weight) values (?,?,?);"
 			<< 20
 			<< "bob"
 			<< 83.0;
 
 		db << "insert into user (age,name,weight) values (?,?,?);"
 			<< 21
-			<< L"jak"
+			<< L"jack"
 			<< 68.5;
 
 		// slects from table user on a condition ( age > 18 ) and executes 
-		// the body of magid_mapper for every row returned .
-		// node : magic_mapper is just a simple macro , the next sample is
-		// equivalent to this one without the use of magic_mapper macro
-		db << "select age,name,weight from user where age > ? ;"
-			<< 18
-			>> magic_mapper(int age, string name, double weight) {
-				cout << age << ' ' << name << ' ' << weight << endl;
-			};
+		// the lambda for every row returned .
 
 		db << "select age,name,weight from user where age > ? ;"
 			<< 18
-			>> function<void(int,string,double)>([&](int age, string name, double weight) {
+			>> [&](int age, string name, double weight) {
 				cout << age << ' ' << name << ' ' << weight << endl;
-			});
+			};
 
-		// i am currently working on a solution to avoid magic mapper
-		// i future i want to this syntax also work 
-		/*
-			db << "select age,name,weight from user where age > ? ;"
-				<< 18
-				>> [&](int age, string name, double weight) {
-					cout << age << ' ' << name << ' ' << weight << endl;
-				};
-		*/
+		// selects the count(*) of table user
+		// note that you can extract a single culumn single row answer only to : int,long,long,float,double,string,wstring
+		int count = 0;
+		db << "select count(*) from user" >> count;
+		cout << "cout : " << count << endl;
 
+		// this also works and the returned value will automatically converted to string
+		string scount;
+		db << "select count(*) from user" >> scount;
+		cout << "scount : " << scount << endl;
 	}
 	catch (exception& e){
 		cout << e.what() << endl;
 	}
+
 }
 ```

example.cpp

@@ -3,61 +3,138 @@
 using namespace  sqlite;
 using namespace std;
 
+/*
+template <typename T>
+struct function_traits
+: public function_traits<decltype(&T::operator())>
+{};
+
+template <typename ClassType, typename ReturnType, typename... Args>
+struct function_traits<ReturnType(ClassType::*)(Args...) const>
+// we specialize for pointers to member function
+{
+enum { arity = sizeof...(Args) };
+// arity is the number of arguments.
+
+typedef ReturnType result_type;
+
+template <size_t i>
+struct arg
+{
+typedef typename std::tuple_element<i, std::tuple<Args...>>::type type;
+// the i-th argument is equivalent to the i-th tuple element of a tuple
+// composed of those arguments.
+};
+};
+
+class database_bind {};
+
+template<int N>
+class A {
+template<typename F>
+static void run(F l);
+};
+
+template<>
+struct A<1> {
+template<typename F>
+static void run(F l) {
+typedef function_traits<decltype(l)> traits;
+typedef typename traits::arg<0>::type type_1;
+
+type_1 col_1;
+get_from_db(0,col_1);
+
+l(col_1);
+}
+};
+template<>
+struct A<2> {
+template<typename F>
+static void run(F l) {
+typedef function_traits<decltype(l)> traits;
+typedef typename traits::arg<0>::type type_1;
+typedef typename traits::arg<1>::type type_2;
+
+type_1 col_1;
+type_2 col_2;
+get_from_db(0,col_1);
+get_from_db(1,col_2);
+
+l(col_1, col_2);
+}
+};
+
+
+void get_from_db(int col_inx, string& str){
+// code to get a column from with col_inx from the database
+// for simplicity
+str = "str_col";
+}
+void get_from_db(int col_inx, int& i){
+// just for simplicity
+i = 12;
+}
+
+
+template<typename F>
+void operator>>(database_bind dbb, F l)
+{
+typedef function_traits<decltype(l)> traits;
+A<traits::arity>::run(l);
+}
+
+*/
+
 int main(){
 	try {
 		// creates a database file 'dbfile.db' if not exists
 		database db("dbfile.db");
 
 		// executes the query and creates a 'user' table
 		db <<
-			"create table user ("
+			"create table if not exists user ("
 			"	age int,"
 			"	name text,"
 			"	weight real"
 			");";
 
 		// inserts a new user and binds the values to ?
-		// note that only types allowed for bindings are 
-		//		1 - numeric types( int ,long ,long long, float, double , ... )
-		//		2 - string , wstring
+		// note that only types allowed for bindings are :
+		//		int ,long, long long, float, double 
+		//		string , wstring
 		db << "insert into user (age,name,weight) values (?,?,?);"
 			<< 20
 			<< "bob"
 			<< 83.0;
 
 		db << "insert into user (age,name,weight) values (?,?,?);"
 			<< 21
-			<< L"jak"
+			<< L"jack"
 			<< 68.5;
 
 		// slects from table user on a condition ( age > 18 ) and executes 
-		// the body of magid_mapper for every row returned .
-		// node : magic_mapper is just a simple macro , the next sample is
-		// equivalent to this one without the use of magic_mapper macro
+		// the lambda for every row returned .
+
 		db << "select age,name,weight from user where age > ? ;"
 			<< 18
-			>> magic_mapper(int age, string name, double weight) {
+			>> [&](int age, string name, double weight) {
 				cout << age << ' ' << name << ' ' << weight << endl;
 			};
 
-		db << "select age,name,weight from user where age > ? ;"
-			<< 18
-			>> function<void(int,string,double)>([&](int age, string name, double weight) {
-				cout << age << ' ' << name << ' ' << weight << endl;
-			});
-
-		// i am currently working on a solution to avoid magic mapper
-		// i future i want to this syntax also work 
-		/*
-			db << "select age,name,weight from user where age > ? ;"
-				<< 18
-				>> [&](int age, string name, double weight) {
-					cout << age << ' ' << name << ' ' << weight << endl;
-				};
-		*/
+		// selects the count(*) of table user
+		// note that you can extract a single culumn single row answer only to : int,long,long,float,double,string,wstring
+		int count = 0;
+		db << "select count(*) from user" >> count;
+		cout << "cout : " << count << endl;
 
+		// this also works and the returned value will automatically converted to string
+		string scount;
+		db << "select count(*) from user" >> scount;
+		cout << "scount : " << scount << endl;
 	}
 	catch (exception& e){
 		cout << e.what() << endl;
 	}
+
 }