How does namespacing work at lower levels with form

my model 'posts' isn't namespaced.

my controller namespaced admin/posts_controller.rb , it's new method looks so:

class admin::postscontroller < applicationcontroller .....  def edit       @post = post.find( params[:id] )   end

why work:

<%= form_for [:admin, @post]  |f| %>

but not this:

<%= form_for @post  |f| %>

how form_for mapping @posts variable?

why autofill form text-areas when namespace there?

a valid @post variable being passed view in both cases.

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