In RoR, f.fields_for is rendering as nothing - forms

Question

I’m using Rails 4.2.7. In my model I have
class MyObject < ActiveRecord::Base
…
belongs_to :address, :autosave => true, dependent: :destroy
accepts_nested_attributes_for :address, :my_object_times
and the address model
class Address < ActiveRecord::Base
belongs_to :state
belongs_to :country
...
has_one :my_object
end
I want to write a form that will allow me to build both the child and parent objects, so I tried
<%= form_for #my_object, :url => my_objects_create_path, :remote => true do |f| %>
<div class="field">
<%= f.fields_for :address do |addr| %>
<%= addr.label :address %> <span name="my_object[address]_errors"></span><br>
City: <%= addr.text_field :city %>
<%= addr.select :state, options_for_select(us_states.collect{|s| [ s.name, s.id ]}), {:prompt => "Select State"} %>
<%= country_code_select('my_object[address]', 'country_id',
[[ 'US', 'United States' ], [ 'CA', 'Canada' ]],
{:include_blank=>true, :selected => #default_country_selected.id},
{:class=>'countryField'}
) %>
<% end %>
</div>
but the above is rendered as only
<div class="field">
</div>
How do I adjust things so that my fields render AND I'm able to create my object in my controller using
my_object = MyObject.new(params)
Edit: Per the answer given, I tried
#my_object.address.build
from teh controller action taht rendres the form, but got the erorr
undefined method `build' for nil:NilClass

Answer 1

#this is in form loading class
def new
#myobject = MyObject.new
#myobject.address = Address.new
end
#Now you can use nested attribute for Address
<%=form_for(#myobject) do |f|%>
<%=f.fields_for :address do |a|%>
Your form fields here
<%end%>
<%end%>
#this is create def
def create
#myobject = MyObject.new(myobject_params)
#myobject.save
end
#in params
def myobject_params
params.require(:myobject).permit(:some, :key,:of, :myobject, :address_attributes[:address, :attribute])
end
#this should work

Answer 2

If my_object has no addresses, then nothing will be rendered. This is default behavior in Rails. One way to get around this is to build one or more empty children in the controller so that at least one set of fields is shown to the user
The Rails guides talk about this in Nested Forms section 9.2
Also, in your MyObject model, i think it should be has_one address. you have belongs_to
class MyObject < ActiveRecord::Base
has_one :address, :autosave => true, dependent: :destroy
accepts_nested_attributes_for :address
end