Do calculation using radio_button variable to nested form controller - Rails 3 - ruby

Question

I have a edit form which I have a radio_button that I would like to pass to a controller action and then use it to do a calculation. In the view I have:
<div class="field">
<%= radio_button_tag(:rating_select, "Up") %>
<%= label_tag(:rating_select, "Good.") %>
<%= radio_button_tag(:rating_select, "Down")%>
<%= label_tag(:rating_select, "Bad.")%>
</div>
In the controller I have:
def rating
#post = Post.find(params[:id])
.....
end
def update
#post = Post.find(params[:id])
##rating_select = params[:rating_select]
if #post.rating_select == "Up"
#post.score += 5
elsif #post.rating_select == "Down"
#post.score -= 5
end
......
end
Currently it is ignoring the if statement so the parameter isn't getting set properly. Ideally I would like to just use a temp variable from the view to use in the if statement to decide if I need to add or subtract in the update. But I also have a rating_select field in post if I need to use it also. Thanks.
UPDATE:
Thanks. That makes sense, I changed it to below but it still isn't incrementing or decrementing the score based on the radio box. So it seems it isn't getting the rating_select?:
def update
#post = Post.find(params[:id])
if params[:rating_select]=="Up"
#post.score += 5
elsif params[:rating_select]=="Down"
#post.score -= 5
end
respond_to do |format|
....
UPDATE2:
Finally figured it out, used another model Ratings to store association. I used the before_save in the Post model and it allowed me to do the calculation and save. What a headache.
before_save :set_rating
def set_rating
if self.rating.rating_select=="Up"
rating.score += 5
elsif self.rating.rating_select=="Down"
rating.score -= 5
end
end

Answer 1

Well, first off, in the code you're showing the post loaded in your update action is not receiving the params from your view.
Your code for an update action should typically look like this:
def update
#post = Post.find(params[:id])
if #post.update_attributes(params[:post])
... do stuff ...
else
render :edit, :alert => 'Unable to update post.'
end
end
Second, since you're using form_tag helper and not form_for, then you're not getting the params all setup for your model (ie. nested under params[:post]). So, in this case, your rating_select option is just a value by itself, which you can test for like this:
if params[:rating_select]=="Up"
...
else
...
end
The big thing to understand from your code is #post doesn't know anything about params[:rating_select], even if you used #post.update_attributes(params[:post]), because radio_button_tag as you have it set up is not building a hash of post attributes, it's just a standalone field.
I hope that makes sense, if you don't understand please leave comments and I'll try to explain more.