Accessing post data in controller

Question

I am iterating through a hash and displaying the values as radio buttons. The hash looks like this:

{
 1=>["a", "b"], 
 2=>["c"], 
 3=>["a", "d", "f", "g"], 
 4=>["q"] ..
}

After selecting the values, the parameters become:

{ "commit"=>"vote", "authenticity_token"=>"db863239855c9f73b9ae54c37f6b92c858acb56f", "1"=>"a", "2"=>"c", "3"=>"d", "4"=>"q"}

How can I access these values (POST data) in the update method of the controller in order to update the count field? I have tried like this.

@votings = Voting.find(:all, :conditions => {params[:k]=>params[:val]})
@votings.each do |voting|
  voting.update_attribute('vote_count',
  voting.vote_count+1)
end

But gives this error:

You have a nil object when you didn't expect it! The error occurred while evaluating nil.each..

Can anybody tell where I went wrong?

Answer 1

The reason you are having serious difficulties is because you are working against the conventions baked into Rails.

Try this for size, although it will require throwing away a lot of code you have already written then wondering about the magic Rails just breathed into your application: http://railscasts.com/episodes/17-habtm-checkboxes

Answer 2

The POST data is stored in the params hash. So if you wanted the value of the parameter 1, you would use params[:1].

Now lets look at :conditions. In the find method, the :conditions parameter can take a hash, which is what you are providing. But your code is saying, take the value of params[:k] and set it to the value of params[:val]. But params[:k] is nil in this example, there is no key :k in your params hash. So when you are searching, you are getting back a nil value for @votings. Trying to use each on a nil gets you your error.