How do I create a Up/Down voting system like stackoverflow?

I'm making a site in Rails, and I want to add a vote up/down system like here in Stackoverflow.

Can anyone suggest how to do it? I do know that I'll enter each vote into the database, but I mean, how do I code the vote buttons? What will I use, can anyone help me. Ajax开发者_如何转开发 isn't required but it would be nice.

I was going to try to use a POST command and do something like this,

<form name="input" action="/grinders" method="POST">
<input type="hidden" name="id" value="<%=h grinder.id %>">
<input type="hidden" name="vote" value="up">
<input type="submit" value="Vote" />
</form>

But, I get an authenticity token error, and I honestly do not know how to work with the form helper.

Have a votes table like so:

[PK] vote_id, vote_type (up/down), [FK] post_id, [FK] user_id, time [optional]

Also add a score field to your posts table

Then you could have the vote button access a link like: /vote/post_id/type/, eg: /vote/14098/up. This can be done with or without Ajax.

When the vote action is called, check if the user has previously voted on that post - if yes, deny it. If not, create a row with the relevant values in the votes table and update the score field in the posts table.