Hey, I'm trying to have a common class to make some database operations, so, I'm using prototype inheritance model, here's the code:

var Barrel = {} || Barrel;

Barrel.DB = function () {
    this.conn = null;
};

Barrel.DB.prototype.setConn = function ( conn ) {
    this.conn = conn;
    return this;
}

Barrel.DB.prototype.insert = function ( table, data ) {
    // this is just a example code.
    var query = "INSERT INTO " + table + " VALUES (?, ?)";
    // I get values from data argument.
    var values = ["val1", "val2"];
    Ti.API.debug( "c: " + this.conn ); // prints: [DEBUG] [3,1732639] c: ti.modules.titanium.database.TiDatabaseProxy@43f45fb8
    this.conn.execute( query, values ); // ERROR!
    return this.conn.lastInsertRowId;
}

function Product() {
    this.setConn( Titanium.Database.open( "my.db" ) );
}

Product.prototype = new Barrel.DB();
Product.prototype.constructor = Product;

var product = new Product();
product.insert( "notices", { col1: "woot", col2: "woot2", col3: null, col4: "null" } );

So, as you see, this.conn actually have an instance of Titanium.Database.DB (ti.modules.titanium.database.TiDatabaseProxy@43f45fb8) but when I try to execute the query I get this error:

[TRACE] I/ALERT ( 725): (kroll$2) [166,1732805] java.lang.IllegalStateException: database not open

The question is: why I can't execute some query even if I have an instance of the database?