```ruby
class Spree::UserSessionsController < Devise::SessionsController
  helper 'spree/users', 'spree/base', 'spree/store'
  if defined?(Spree::Dash)
    helper 'spree/analytics'
  end

  include Spree::Core::ControllerHelpers::Auth
  include Spree::Core::ControllerHelpers::Common
  include Spree::Core::ControllerHelpers::Order
  include Spree::Core::ControllerHelpers::SSL

  ssl_required :new, :create, :destroy, :update
  ssl_allowed :login_bar

  def create
    authenticate_spree_user!

    if spree_user_signed_in?
      respond_to do |format|
        format.html {
          flash[:success] = Spree.t(:logged_in_succesfully)
          redirect_back_or_default(after_sign_in_path_for(spree_current_user))
        }
        format.js {
          user = resource.record
          render :json => {:ship_address => user.ship_address, :bill_address => user.bill_address}.to_json
        }
      end
    else
      flash.now[:error] = t('devise.failure.invalid')
      render :new
    end
  end

  def destroy
    env['warden'].logout(:spree_user)
    super
  end

  def nav_bar
    render :partial => 'spree/shared/nav_bar'
  end

  private
    def accurate_title
      Spree.t(:login)
    end

    def redirect_back_or_default(default)
      redirect_to(session["spree_user_return_to"] || default)
      session["spree_user_return_to"] = nil
    end
end
```

Fix setting logout flash message by simply letting devise handle destroy action.
user
```ruby
class Spree::UserSessionsController < Devise::SessionsController
  helper 'spree/users', 'spree/base', 'spree/store'
  if defined?(Spree::Dash)
    helper 'spree/analytics'
  end

  include Spree::Core::ControllerHelpers::Auth
  include Spree::Core::ControllerHelpers::Common
  include Spree::Core::ControllerHelpers::Order
  include Spree::Core::ControllerHelpers::SSL

  ssl_required :new, :create, :destroy, :update
  ssl_allowed :login_bar

  def create
    authenticate_spree_user!

    if spree_user_signed_in?
      respond_to do |format|
        format.html {
          flash[:success] = Spree.t(:logged_in_succesfully)
          redirect_back_or_default(after_sign_in_path_for(spree_current_user))
        }
        format.js {
          user = resource.record
          render :json => {:ship_address => user.ship_address, :bill_address => user.bill_address}.to_json
        }
      end
    else
      flash.now[:error] = t('devise.failure.invalid')
      render :new
    end
  end

  def nav_bar
    render :partial => 'spree/shared/nav_bar'
  end

  private
    def accurate_title
      Spree.t(:login)
    end

    def redirect_back_or_default(default)
      redirect_to(session["spree_user_return_to"] || default)
      session["spree_user_return_to"] = nil
    end
end
```
assistant