title: Create action always creates two identical table entries instead of one
body: <p>I have a create action in my ProductsController (the params come from a form in my view):</p>
  
  <pre><code>def create
    vendor = @current_vendor
    product = Product.create(:name =&gt; params[:product][:name])
    vendor.products &lt;&lt; product
    vendor.belongings.create(:product_id =&gt; product.id, :count =&gt; params[:belonging][:count], :detail =&gt; params[:belonging][:detail])
    if vendor.save
      flash[:notice] = "Produkt hinzugefügt!"
      redirect_back_or_default root_url
    else
      render :action =&gt; :new
    end
  end
  </code></pre>
  
  <ol>
  <li>It creates a variable "vendor", which stores the currently logged-in vendor (Authlogic)</li>
  <li>A new Product is created (the product name is from the input field in the form) and stored in the variable "product"</li>
  <li>The "product" is being connected to the current vendor</li>
  <li>In the belongings table, additional informations to the product are being stored</li>
  <li>it saves the whole thing</li>
  </ol>
  
  <p>It's a many-to-many relationship throught the belongings table.</p>
  
  <p><strong>My problem is, the create action always creates the product twice!</strong></p>
  
  <p>Thanks for your help! :)</p>
  
  <p>My console log when I create a new object through my form is:</p>
  
  <pre><code>Started POST "/products" for 127.0.0.1 at 2013-09-15 20:40:26 +0200
  Processing by ProductsController#create as HTML
    Parameters: {"utf8"=&gt;"✓", "authenticity_token"=&gt;"lNk/qQMP0xhlCuGgHtU+d5NEvIlCFcPSKB0FxDZH0zY=", "product"=&gt;{"name"=&gt;"Erdbeeren"}, "belonging"=&gt;{"count"=&gt;"20", "detail"=&gt;"Rot"}, "commit"=&gt;"Create"}
  DEPRECATION WARNING: ActiveRecord::Base#with_scope and #with_exclusive_scope are deprecated. Please use ActiveRecord::Relation#scoping instead. (You can use #merge to merge multiple scopes together.). (called from current_vendor_session at /Users/reto_gian/Desktop/dici/app/controllers/application_controller.rb:11)
    Vendor Load (0.3ms)  SELECT "vendors".* FROM "vendors" WHERE "vendors"."persistence_token" = '04f75db0e2ef108ddb0ae1be1da167536d47b4d79c60ecb443ad2ea5717ecd752388e581f9379746568c72372be4f08585aa5581915b1be64dc412cded73a705' LIMIT 1
     (0.1ms)  begin transaction
    SQL (0.8ms)  INSERT INTO "products" ("created_at", "name", "updated_at") VALUES (?, ?, ?)  [["created_at", Sun, 15 Sep 2013 18:40:26 UTC +00:00], ["name", "Erdbeeren"], ["updated_at", Sun, 15 Sep 2013 18:40:26 UTC +00:00]]
     (0.8ms)  commit transaction
     (0.1ms)  begin transaction
    SQL (0.6ms)  INSERT INTO "belongings" ("created_at", "product_id", "updated_at", "vendor_id") VALUES (?, ?, ?, ?)  [["created_at", Sun, 15 Sep 2013 18:40:26 UTC +00:00], ["product_id", 7], ["updated_at", Sun, 15 Sep 2013 18:40:26 UTC +00:00], ["vendor_id", 1]]
     (0.9ms)  commit transaction
     (0.1ms)  begin transaction
    SQL (0.6ms)  INSERT INTO "belongings" ("count", "created_at", "detail", "product_id", "updated_at", "vendor_id") VALUES (?, ?, ?, ?, ?, ?)  [["count", "20"], ["created_at", Sun, 15 Sep 2013 18:40:26 UTC +00:00], ["detail", "Rot"], ["product_id", 7], ["updated_at", Sun, 15 Sep 2013 18:40:26 UTC +00:00], ["vendor_id", 1]]
     (0.9ms)  commit transaction
  Redirected to http://localhost:3000/
  Completed 302 Found in 30ms (ActiveRecord: 5.1ms)
  </code></pre>