Editing a form using fields_for in Rails

post.rb

# app/models/post.rb

class Post < ActiveRecord::Base
  has_many :tags, dependent: :destroy
  
  # Enable the building of complex forms
  accepts_nested_attributes_for :tags, allow_destroy: true
end

tag.rb

# app/models/tag.rb

class Tag < ActiveRecord::Base
  belongs_to :post
end