Question

I wonder if there is a method that returns all child objects of an object, or create a new child object if none of them exists.

Such a method is convenient for creating nested form, where it often the case that because a child object has not been initialized that the nested form does not show up.

Thank you.

Answer 1

I do this in nested forms:

<%= form_for @parent do |f| %>
  ...
  <%= f.fields_for @parent.children || @parent.children.build do |child| %>
    ...
  <% end %>
  ...
<% end %>

or wrap it as a model method:

class Model < AR::Base
  ...
  def children_form
    children || children.build
  end
end

then use it in form

<%= f.fields_for @parent.children_form do |child| %>