Question

I made a simple inventory system, and want to display a selector to choose the size before buying the product. I want the selector to only show the items that are in stock, and not allow the user to choose the ones that aren’t. I made it so that when the product is created, it creates a set of variants, with their name and quantity. So when I create a product, it creates 3 variants named Small, Medium, and Large, each with a qty of 0. I used the ruby console to update the qty of each variant so the below would work:

views/product/show.html.erb

<div class="size"><br/>Size: <%= f.select(:size, options_for_select(@sizes_availiable), :prompt => "Select a size") %></div>

product_controller.rb

  def show
    @product = Product.find(params[:id])
    @sizes_availiable = Product.build_size_enum( @product.id )
  end

Product.rd

  def self.build_size_enum(product_id)
    p = Product.find(product_id)
    a = []
    p.variants.each do |var|
      unless var.qty = 0
        a << var.name
      end
    end
    a
  end

However, the options are empty (with only the option “Select a size”). If I remove the unless statement (which defeats the purpose) from Product.rb so the method looks like below, the list populated with small medium and large:

Product.rd

  def self.build_size_enum(product_id)
    p = Product.find(product_id)
    a = []
    p.variants.each do |var|
      a << var.name
    end
    a
  end

Any ideas on why the unless statement is causing a problem?

Answer 1

You are using = instead of ==. var.qty = 0 will always test as “true” in Ruby, with the unfortunate side effect of wiping out the data you are trying to test. Change that to var.qty == 0 and you should be fine.