Select Tag, undefined method `map' - forms

Question

I have a subscriptions form where I am trying to set the plan the user has chosen, the business they would like to associate with the subscription and the payment details. In my form I use a select tag to display a list of all of the businesses and it displays properly in my view but upon save I get the following error:
undefined method `map' for #<Business:0x007f8ea7955b90>
new.html.erb
<div class="field">
<%= select_tag :business_id, options_from_collection_for_select(#businesses, "id", "name") %>
</div>
subscriptions_controller.rb
...
def new
#subscription = Subscription.new
#plan = Plan.find(params["plan_id"])
#businesses = Business.all
end
def create
#subscription = Subscription.new(subscription_params)
raise "Please, check subscription errors" unless #subscription.valid?
#subscription.process_payment
#subscription.save
redirect_to #subscription, notice: 'Subscription was successfully created.'
rescue => e
flash[:error] = e.message
render :new
end
private
def set_subscription
#subscription = Subscription.find(params[:id])
end
def subscription_params
params.require(:subscription).permit(:plan_id, :business_id, :card_token, :coupon)
end
Am I setting up the select_tag properly? Do I need to fix my create method? Looked at other solutions on SO with little success.

Answer 1

Rails instantiates a new controller for every request. There's some information about that here.
This means that any instance variables you've set in new won't be available when you process the POST in create.
In your case, you are rendering the :new template in the rescue block of the create action when the new subscription fails validation. You're only getting the error at this point, not when you originally access the form.
The problem is that render :new doesn't call the new action; it just renders the template. In the case where the subscription fails validation and the form is re-rendered, the new action has never been called by this controller instance, and the instance variables do not have the values expected by the template.
Try this instead of render :new:
redirect_to new_subscription_url
This will instantiate a new controller and call the new action, so that you will be starting over with a clean slate. The instance variables needed in the new template will be assigned the correct values before the template is rendered.
As an alternative, you could set the instance variables in the rescue block:
def create
...
rescue => e
flash[:error] = e.message
#businesses = Business.all
render :new
end
Here's a similar question on Stack Overflow.
Hope that helps. Happy coding!