*begin(stmt) fails with single row results

[xiptos]

I believe trying to get a row from a single row query result will result in:

Process finished with exit code 139 (interrupted by signal 11: SIGSEGV)

when using begin(stmt) to retrieve the rowIterator.

Example:

    try {
        //Creates a SQLite connection object
        Sqlite::SqliteConnection connection("myProfile.db");

        // sqliteExecute(connectionOb, "query"); executes a SQLite query, in this case creates a table
        sqliteExecute(connection, "create table if not exists myResume (skills text, proficiency int DEFAULT 5)");

        sqliteExecute(connection, "insert into myResume(skills, proficiency ) values (?, ?)", "C++", 7);

        auto stmt = Sqlite::SqliteStatement(connection, "select skills, proficiency from myResume");
        stmt.execute();
        auto row = *begin(stmt);
        std::cout << typeid(row).name() << std::endl;
        std::cout << std::left << std::setw(8) << row.getString() << " : " << row.getInt(1) << std::endl;
    }
    catch (const Sqlite::exception &e) {
        std::cout << e.errorMessage_ << '(' << e.errorCode_ << ')';
    }

[geekyMrK]

The problem doesn't arise in auto row = *begin(stmt);, the problem is in next line, cpp std::cout << typeid(row).name() << std::endl;
As you are asking for the typeid of the row. which it currently didnt support yet.

there is a better way to do get a single row:

Sqlite::SqliteStatement stmt(connection, "select skills, proficiency from myResume"); 
stmt.execute();
std::cout << std::left << std::setw(8) << stmt.getString() << " : " << stmt.getInt(1) << std::endl;
//As the SqliteStatement class also has `get()` methods

Some implementation notes (if you are curious about the type of row object):
1.) I use CRTP (Curiously Recurring Template Pattern which has zero runtime overhead) in which i have a base class SqliteReader. The SqliteReader has all the get() methods. The SqliteStatement and SqliteRow class inherit from the SqliteReader.
2.) The begin(SqliteStatement) method returns rowIterator class. rowIterator class just hold a pointer to SqliteStatement class. So, it's just a light-weight class to check whether the SqliteStatement has more results to show.
3.) The type you get by dereferencing the begin(SqliteStatement) is the rowIterator, but when you dereferencing it by using *begin(), you get a proxy type SqliteReader Class.
4.) SqliteReader Class (as discussed in note 1) is inherited from SqliteReader Class. It is a lightweight class(uses CRTP) just contains a raw sqlite3_stmt * designed to iterate over the for loop (just has get() ) methods to retrieve the result.

This is done to make it simple yet efficient (almost zero cost abstraction) C++ Wrapper over SQLite3 🙂

[xiptos]

Got it! Thank you, @geekyMrK. Very nice approach! :)