Ndtyjky

I'm creating a database of products and want to check when a new product is created, if that product already exists.

99% of the time, the product should have a unique product code, but sometimes this will not be the case when a revised version comes out with the same product code.

I would like to have it so that the database checks if the product code exists already. If it does, then the user can either go ahead and create the product anyway, go to the product that already exists, or cancel.

I am trying to achieve this in the controller but cannot seem to get the syntax of the exists? method correct. Can someone point out where I am going wrong, please?

def create

    @product = Product.new(product_params)



    if Product.product_code.exists?(@product.product_code)

        render 'new'

        flash[:error] = "This product already exists."



    elsif @product.save

        redirect_to @product

    else

        render 'new'

    end



end

Instead if Product.product_code.exists?(@product.product_code) possibly you should use if @product.product_code.present?

UPD: thanks to all, commented below.

Correct use of exists? is Product.where(product_code: @product.product_code).exists?

You should note that what you are doing in the controller or adding a standard uniqueness validation to the model will not allow duplicate Products to be created at all.

This will just keep sending the user back to the form:

def create

  @product = Product.new(product_params)

  if Product.exists?(product_code: @product.product_code)

    render 'new'

    flash[:error] = "This product already exists."

  elsif @product.save

    redirect_to @product

  else

    render 'new'

  end

end

If you want to simply warn the user once you can attach a virtual attribute on the model and use it as condition for the validation:

class Product < ApplicationRecord

  attribute :dup_warning, :boolean, default: true

  validate :lax_product_code_uniquenes



  def lax_product_code_uniqueness

    if new_record? && !dup_warning && Product.exists(product_code: self.product_code)

      errors.add(:product_code, 'is not unique - are you sure?')

      self.dup_warning = true

    end

  end

end

Then add the virtual attribute to the form:

<%= form_with(model: @product) do |f| %>

  ...

  <%= f.hidden_input(:dup_warning) %>

  ...

<% end %>

And you don't need to really do anything in the controller besides add dup_warning to the params whitelist.

def create

  @product = Product.new(product_params)

  if @product.save

    redirect_to @product

  else

    render 'new'

  end

end



def product_params

  params.require(:product)

        .permit(:foo, :bar, :product_code, :dup_warning)

end