Question

i have a simple dropdown like :

<%= collection_select("user_cities", "city_id", current_user.cities, :id, :name ) %>

current_user.cities is an array of the user cities. Each city has a field named “is_primary” and only one city has it set as true.

My question is, how can i make the above collection_select(or transform it if needed), so that it picks the selected option, based on City.is_primary ?

Answer 1

From the docs:

By default, post.person_id [in your case user_cities.city_id] is the selected option. Specify :selected => value to use a different selection or :selected => nil to leave all options unselected.

Armed with that knowledge we can pass the appropriate option to collection_select:

<%= collection_select "user_cities", "city_id", current_user.cities, :id, :name,
      :selected => current_user.cities.detect(&:is_primary).id
%>