ActionView::FormModel

Underscored singular model name ("post") — the polymorphic-path input: [user, post] persisted → user_post_path(user, post), new → user_posts_path(user). May differ from form_scope for namespaced models, hence a separate method.

Nested-attributes associations for FormBuilder#fields_for — the counterpart of AR's accepts_nested_attributes_for. Override to return the child records of assoc; nil (default) means the name is not a nested-attributes association and fields_for falls back to plain scope nesting.