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11.4 Refactor CircleDao

  1. Change the first lines of the CircleDao class definition: 

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    public class CircleDao : AbstractDao
{
    public CircleDao(DbAccess dbAccess) : base(dbAccess)
    {
    }

  2. Add a helper method below SaveCircle: 

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    private int SaveShape(string color)
{
    string sql = "INSERT INTO Shape(color) VALUES (@color);";
    int primaryKey = 0;
    try
    {
        var cmd = new MySqlCommand(sql, _dbAccess.GetConnection());
        cmd.Parameters.AddWithValue("@color", color);
        cmd.ExecuteNonQuery();
        cmd.CommandText = "SELECT LAST_INSERT_ID();";
        primaryKey = Convert.ToInt32(cmd.ExecuteScalar());
    }
    catch (MySqlException ex)
    {
        Console.WriteLine(ex);
    }
    return primaryKey;
}

  3. Simplify the SaveCircle method: 

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    public void SaveCircle(Circle circle)
{
    int primaryKey = SaveShape(circle.Color);
    string sql = "INSERT INTO Circle VALUES (@id, @radius, @x, @y);";
    try
    {
        var cmd = new MySqlCommand(sql, _dbAccess.GetConnection());
        cmd.Parameters.AddWithValue("@id", primaryKey);
        cmd.Parameters.AddWithValue("@radius", circle.Radius);
        cmd.Parameters.AddWithValue("@x", circle.Center.X);
        cmd.Parameters.AddWithValue("@y", circle.Center.Y);
        cmd.ExecuteNonQuery();
    }
    catch (MySqlException ex)
    {
        Console.WriteLine(ex);
    }
}

  4. Add the following UML class diagram:

    Mermaid diagram Mermaid diagram

    The PointDao and CircleDao classes are subclasses of AbstractDao. Therefore, these classes have access to the attributes of AbstractDao.

    • They also have access to the shared methods used to handle SQL statements.
    • The PointDao class only contains methods that are specific to objects of the Point class.
    • The CircleDao class only contains methods that are specific to objects of the Circle class.

  5. Change the code in your Main method: 

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    DbAccess dbAccess = new DbAccess("Server=localhost;Database=Shapes;User=userShapes;Password=userShapesPW;");
dbAccess.OpenConnection();

PointDao pointDao = new PointDao(dbAccess);
pointDao.SavePoint(new Point(8, -12));
foreach (Point point in pointDao.GetPoints())
    Console.WriteLine(point);

CircleDao circleDao = new CircleDao(dbAccess);
circleDao.SaveCircle(new Circle(6.5, new Point(-2.3, -1.3), "purple"));

dbAccess.CloseConnection();

  6. Run your program and verify in Workbench that the point and circle were added.