[Ken Koontz]

I have an 'action', which is an object that is the controlling code for incoming requests. My code looks like this:

    loginSubmit: function() {

        var self = this,

            session = generateCookie();

        user.on('loginValid', function(data) {

            client.sadd('sessions', session, redis.print);

            self.response.setHeader("Set-Cookie", ["session="+session+";Path=/"]);

            self.response.writeHead(200);

            self.response.end();

        }); 

        user.on('loginInvalid', function(data) {

            self.statusCode(404);

        }); 

        user.login(self.postData.email, self.postData.password);

    },  

'loginSubmit' is the action, it is executed when a request comes into /login/submit. Currently only AJAX requests touch loginSubmit, no page reload.

When I fill the form and hit submit, ajax fires and runs loginSubmit. If I fill out the form to emit 'loginInvalid', then fill it out again to emit 'loginValid', node throws an error:

http.js:686

    throw new Error('Can\'t render headers after they are sent to the client.'

Why?