What are the edit and new actions doing in this code?

I have three models:

class Country < ActiveRecord::Base
  has_many :regions
  has_many :assets, :dependent => :destroy
  accepts_nested_attributes_for :assets
end


class Region < ActiveRecord::Base
  belongs_to :country
  has_many :appartments

  has_many :assets, :dependent => :destroy
  accepts_nested_attributes_for :assets
end


class Asset < ActiveRecord::Base
  belongs_to :region
  belongs_to :country
  has_attached_file :image,
    :styles => {
      :thumb=> "100x100开发者_运维知识库>",
      :small  => "300x300>",
      :large => "600x600>"
  } 
end

Can some explain to me what the edit and new method/action is of the region controller, to store the asset(image)?

Here is an example of how you could do it by building your form in a certain way. It should work for both the new and update actions.

<%= form_for @region do |f| %>
  <%= f.fields_for :assets, @region.assets.build do |fa| %>
    <%= fa.file_field :image %>
  <% end %>
<% end %>

What this does is to first create the form for the @region instance. And since you have the accepts_nested_attributes_for :assets you can use the fields_for method to work with the associations. The symbol :assets tells it which association to read from, but since you want to add a new image and not work with the existing, you can add the second argument which is a single new Asset instance created by the build method.

And then finally you can add the file_field to actually upload the file.

If you build your form this way you should not have to alter the action code inside your controller at all.

Edit:

And here is how the new and create actions could look like to make the view work:

def new
  @region = Region.new
  # Add respond_to or respond_with if you want
end

def create
  @region = Region.new(params[:region])
  if @region.save
    render :action => :show
  else
    render :action => :new
  end
end