Question

I have this code which is part of my User Class. When I call this function:

user = new User();
user.regUser("john", "[e-mail]", "john123", function() { });

I get the error

Uncaught TypeError: Object #<Database> has no method 'writeDb'

The function in the User Class:

User.prototype.regUser = function(name, email, password, cb) {
        this.db.exec("SELECT * from users WHERE user_email='"+email+"';", function(results) {
            var len = results.rows.length;
            if (typeof(cb) == 'function') {
                if (len < 1) {

                    this.name = name;
                    this.email = email;
                    this.password = password;
                    this.writeDb();

                    cb(true); // username doesn't exists

                } else {
                    cb(false); // username already exists
                }
            }
        });
    }

Is the problem maybe that the ‘this’ variables are called in a nested function of my function? Because in other function is works when not nested. How can I fix this?

• little edit:
  I’ve written this.db.writeDb() which has to be this.writeDb()
  Still get the error though.

Answer 1

You were assuming “this” object is a User class in callback. Just declare a closure variable to capture “this” object. Try this;

User.prototype.regUser = function(name, email, password, cb) {
      var user = this;
      user.db.exec("SELECT * from users WHERE user_email='"+email+"';",   function(results) {
        var len = results.rows.length;
        if (typeof(cb) == 'function') {
            if (len < 1) {

                user.name = name;
                user.email = email;
                user.password = password;
                user.db.writeDb();

                cb(true); // username doesn't exists

            } else {
                cb(false); // username already exists
            }
        }
    });
}