I have my problem, kinda solved, but I think its a bit clumsy way, so hope to get a better way, as well as a better understanding whats going on here.
_form.html.erb:
<%= select_tag(:category_id, options_for_select(@categories), :prompt => "Select one!") %>
products_controller.rb:
def new
@product = Product.new
@categories = Category.all.map { |c| [ c.name, c.id ] }
end
If user submits form without selecting any of the select_tag options he gets undefined method 'map' for nil:NilClass error.
I know that it comes since my @categories is nil, but I cant figure how to avoid that..?
My final solution, that is working:
<%= select_tag(:category_id, options_for_select(@categories || Category.all.map { |c| [ c.name, c.id ] }), :prompt => "Select one!") %>
But I feel there is a better way. Also I think, that by assigning a default select_tag value with :selected might work as well, but I couldnt implement it with my knowledge of Ruby syntax...
Please try this way of select_tag:
select_tag(:category_id, options_from_collection_for_select(Category.all, :id, :name), include_blank: "Select Category")
Let me know if you face any issue..