无法弄清楚为什么表单无法保存到Rails上的数据库ruby中

Question

I am trying to save a "product" aka pair of glasses to a database with the following data fields-- Name, Lens, Frame, Temple, Accent, Quantity, Photo.

app/controllers/product_controller.rb

def create
   @product = Product.create(product_params)

end

# Each pair of glasses has a name, lens, frame, accent, quantity, and picture
def product_params
   params.require(:product).permit(:name, :lens_id, :frame_id, :temple_id, :accent_id, :quantity, :photo)
end

app/views/products/_form.html.erb

<div class="field">
    ....
    <%= f.label :quantity %>
    <%= number_field_tag :quantity, nil, class: 'form-control', min: 1
</div>  

I can save the record and everything saves to the database except quantity which saves as 'nil'. I can go into the rails console, select that record, and manually add a quantity via the console though... what am I missing?

Thanks in advance!

Answer 1

The error is a result of the helper tag you are using for :quantity . You should be using the form builder helper number_field and not the generic number_field_tag .

It should look like this:

<%= f.number_field :quantity, nil, class: 'form-control', min: 1 %>

If this isn't working for you, perhaps due to your version of Rails, you can override the type attribute on text_field and try:

<%= f.text_field :quantity, nil, class: 'form-control', type: :number, min: 1 %>

---

If you want to know why, you will need to understand how Rails is building the POST form data. Using the form builder form_for you will see that all of the form fields follow the convention object_class[attribute] . In your example it'd make product[name] , product[lens_id] , etc...

By using number_field_tag it created an input with the name quantity but you need it to be product[quantity] so that when you call Product.create(product_params) it includes that provided value.

Your code is producing this for the params:

 { 
   product:  
   {
     name: '...',
     lens_id: 1
   },
   quantity: 1
 }

vs what is expected:

{
  product:
  {
    name: '...',
    lens_id: 1,
    quantity: 1
  }
}