如何在我的应用程序中实现装饰器？

Question

我正在尝试在我的应用程序中实现this。

这篇文章说我必须创建一个装饰器，但它并没有详细说明如何做到这一点。代码如下：

module CartDecorator
  extend ActiveSupport::Concern

  module InstanceMethods
    def is_downloadable?
      items = self.items.collect { |li| li[:variant].item }
      items.all? { |i| i.is_downloadable }
    end

    def has_downloadable?
      items = self.items.collect { |li| li[:variant].item }
      items.any? { |i| i.is_downloadable }
    end
  end
end

Piggybak::Cart.send(:include, CartDecorator)

我试着运行rails g decorator Cart，但不起作用。

我所做的就是将上面的代码放在app/helpers/cart_helper.rb中。

然后，当我尝试运行rails g command (为了其他目的)时，我现在得到了这个错误：

/.rvm/gems/ruby-2.0.0-p0@myapp/gems/activesupport-3.2.13/lib/active_support/inflector/methods.rb:230:in `block in constantize': uninitialized constant CartHelper (NameError)
    from /.rvm/gems/ruby-2.0.0-p0@myapp/gems/activesupport-3.2.13/lib/active_support/inflector/methods.rb:229:in `each'
    from /.rvm/gems/ruby-2.0.0-p0@myapp/gems/activesupport-3.2.13/lib/active_support/inflector/methods.rb:229:in `constantize'
    from /.rvm/gems/ruby-2.0.0-p0@myapp/gems/activesupport-3.2.13/lib/active_support/core_ext/string/inflections.rb:54:in `constantize'
    from /.rvm/gems/ruby-2.0.0-p0@myapp/gems/actionpack-3.2.13/lib/abstract_controller/helpers.rb:136:in `block in modules_for_helpers'
    from /.rvm/gems/ruby-2.0.0-p0@myapp/gems/actionpack-3.2.13/lib/abstract_controller/helpers.rb:131:in `map!'

解决这个问题的最好方法是什么？

Answer 1

您应该将上述代码添加到app/decorators/cart_decorator.rb中

装饰器文件夹将是新的，并在启动rails应用程序时自动加载。当它运行Piggybak::Cart.send(:include, CartDecorator)时，它会用你上面声明的方法装饰你的Piggybag::Cart。