Submitting custom information to a controller

This is probably simple, but I've tried a few things and couldn't find a way to make it work.

I would like to update a model with custom information given in a form_for

To make it more concrete, I'm on the show page for a particular instance of MyClass and I would like to pass something like the string "yay" into the controller, and then do as I please with the input. Maybe pass it back to the page as a flash message, o开发者_高级运维r maybe modify the contents and then store it as a field of the MyClass instance.

I can write form_for's that contain the attributes of MyClass without prbolems, but it seems that other fields throw an error.

How do I write the form_for so that I can accomplish one of the two above scenarios?

  def update
    @my_class = MyClass.find(params[:id])
    flash[:notice] = "This works" # but what can I write in a form for for it to be a variable that's passed in?
    #rest of the update
  end

Form helpers that unitize a form builder instance (like f.text_field) expect a valid model attribute so it can generate the appropriate id and populate the field with data from the model. If you want to have form fields that do not correspond to model attributes, don't use the the standard f.text_field but instead use:

<%= text_field_tag 'my_custom_tag' %>

which should render something like:

<input type="text" id="my_custom_tag"></input>

When the form is submitted, the value of the input will show up in the params hash with a key of :my_custom_tag.

I hope this helps.

It seems that you would probably need a hidden_field in your form :

http://apidock.com/rails/ActionView/Helpers/FormHelper/hidden_field

However, if you wish to save some kind of state, which seems like this is what you want, you would never use that. Instead, you would use a session. The reason is that a hidden field can be manipulated by the client and thus security can easily be overridden.

Like Spyros said, a hidden field will give you the place. Assuming you are ok with the fact that a user can modify the URL, just add attr_accessor :foo to your model.

In the controller you can access it with bar = params[:foo] and do as you please.