How do I change the form rendered by Rails? - ruby-on-rails

Question

I have two classes, User and Contact. A User has many contacts, and a Contact belongs to a user. In the user's show view, I have:
<%= link_to 'Add Contact', :controller => "contacts", :action => "new", :user => #user.id %>
Then, in the contact's controller, under the new action, I have:
#user = User.find(params[:user])
#contact = Contact.new
#contact.user = #user
When the new contact form renders, it has #<User:0x4c52940> in the User field already. However, when I go to submit the form, I get the error: User(#39276468) expected, got String(#20116704).
The problem is that, when create gets called, Ruby takes everything in the form and overwrites the fields in the new Contact. So: how can I change the form to remove the User field, so that the User is not overwritten with the string?
Edit:
My Contact's new.html.erb has this:
<%= render 'form' %>
<%= link_to 'Back', contacts_path %>
Contact's controller:
def new
#user = User.find(params[:user])
#contact = Contact.new
#contact.user = #user
respond_to do |format|
format.html # new.html.erb
format.json { render json: #contact }
end
end
and
def create
#contact = Contact.new(params[:contact])
respond_to do |format|
if #contact.save
format.html { redirect_to #contact, notice: 'Contact was successfully created.' }
format.json { render json: #contact, status: :created, location: #contact }
else
format.html { render action: "new" }
format.json { render json: #contact.errors, status: :unprocessable_entity }
end
end
end

Answer 1

I believe you misuse create action of the controller. Essentially its content should be like so
def create
#user = User.find(params[:user_id])
contact = #user.contacts.build(params[:contact])
if contact.save
flash[:alert] = 'New contact is created'
redirect_to contacts_path(contact)
else
flash.now[:error' = 'Error creating contract'
render :action => :new
end
end
So +1 for the previous answer - show you controller and new form code