Nested forms

Para allows you to create nested forms through its nested fields feature.

When you have a has_many or has_one relation associated with a accepts_nested_attributes_for call, Para automatically detects it as a nested form.

Usage

You need to use the custom input type :nested_many in your field.

Let's say you have a car model with nested wheel instances :

class Car < ActiveRecord::Base
  has_many :wheels
  accepts_nested_attributes_for :wheels  
end

You can the use in your Para form :

= para_form_for(resource) do |form|
  = form.input :wheels, as: :nested_many

You'll be presented with a nested form for the wheels.

You can also use : accepts_nested_attributes_for :wheels, allow_destroy: :true, a "remove" button will be added to the nested fields.

For Nested has_one relations, juste use the :nested_one input type.

Nested form fields

When you have a nested model, using accepts_nested_attributes_for, Para will automatically allow you to add / edit and delete thos nested resources withing the parent form

If you want to override the nested form behavior, you can generate the fields with :

rails g para:nested_fields <your_model_name>

You can pass --container or -c option to generate the container partial used for nested many relations to customize collapsed panels, reordering handles, etc.

Nested form Single table inheritance (STI) fields

When the relation model is parent of other models (i.e. you have an STI structure) para will present you with a dropdown to choose which subclass you want to instantiate when creating your nested resource.

class Car < ActiveRecord::Base
  has_many :wheels, class_name: 'Wheel::Base'
  accepts_nested_attributes_for :wheels  
end

class Wheel::Base < ActiveRecord::Base
end

class Wheel::Rounded < Wheel::Base
end

class Wheel::Squared < Wheel::Base
end

In the form, the add button will present you with a dropdown, allowing you to choose between "Rounded" and "Squared".

You can use the usual I18n (activerecord.models.<model_name>) keys to change and translate the subclasses names in the dropdown.

Also, this feature supports "partial inheritance", which allows you to create any of : app/views/admin/wheel/squareds/_fields or app/views/admin/wheel/bases/_fields to overrided the nested fields for that model.