rails wrong number of arguments (given 9, expected 0) with form model

I'm using this to build a form model (i want to create a Transaction and an Address, and the address must belong to the transaction). I'm getting a rails wrong number of arguments (given 9, expected 0) error, and cannot figure out why. The error is in the controller params, but I'm not sure why it's expecting 0. My form model looks like this:

class TransactionForm
 include ActiveModel::Model

 attr_accessor :sender_id, :recipient_id, :item_id, :asking_price, :amount, :sender_agreement, :name, :street, :street_2, :state, :zip_code, :phone_number


 validate :sender_id
 validate :recipient_id
 validate :item_id
 validate :asking_price
 validates :amount, presence: true
 validates :sender_agreement, presence: true
 validates :name, presence: true
 validates :street, presence: true
 validates :street_2, presence: true
 validates :state, presence: true
 validates :zip_code, presence: true
 validates :phone_number, presence: true

 def save
  if valid?
   address = create_address
   transaction = create_transaction(address)
  end
 end

 private
 def create_address
  Address.create(name: name, street: street, street_2: street_2, state: state, 
                                    zip_code: zip_code, phone_number: phone_number)
 end

 def create_transaction(address)
  Transaction.create(sender_id: sender_id, recipient_id: recipient_id, item_id: item_id, asking_price: asking_price, amount: amount, sender_agreement: sender_agreement, sender_signed_at: Time.now, address: address)
 end
end

And my controller's #show and #create actions and whitelisted params look like this:

#this action is in a separate ItemsController, tho that doesn't really matter
def show
 @transaction = TransactionForm.new
end

#this action is in TransactionsController
def create
 @transaction = TransactionForm.new(transaction_params)
 if @transaction.save
  redirect_to item_path(@transaction.item), notice: "approved"
 else
  redirect_to item_path(@transaction.item), notice: "error"
 end
end

def transaction_params
 params.require(:transaction_form).permit!(:amount, :asking_price, :sender_agreement, :name, :street, :street_2, :state, :zip_code, :phone_number)
end

My form basically looks like this:

<%= form_for @transaction, url: transactions_path do |f| %>
 <%= f.hidden_field :sender_id, value: current_user.id %>
 <%= f.hidden_field :recipient_id, value: @item.owner.id %>
 <%= f.hidden_field :item_id, value: @item.id %>
 <%= f.hidden_field :asking_price, value: @item.price %>
 <%= f.text_field :amount %>
 <%= f.text_field :name %>
 <%= f.text_field :street %>
 <%= f.text_field :street_2 %>
 <%= f.text_field :state %>
 <%= f.text_field :zip_code %>
 <%= f.text_field :phone_number %>
 <%= f.check_box :agreement %>
 <%= f.submit "submit" %>
<% end %>

This looks more or less exactly like the code in the blog post, but for some reason it's expecting 0 args. Why is this?

params.permit! whitelists all attributes -> Rails permit!

You should use permit