ruby-on-rails-3 - 如何在 Rails 引擎中创建关注点？

Question

我正在尝试在引擎内部创建一个关注点，以便在将安装此引擎的主应用程序中添加/覆盖此功能。问题是我遇到了问题，包括引擎模块中的问题。 Rails 似乎找不到它。

这是我的post.rb文件在 app/models/blorgh/post.rb :

module Blorgh
  class Post < ActiveRecord::Base
    include Blorgh::Concerns::Models::Post
  end
end

这是我的 post.rb关注 lib/concerns/models/post.rb :

需要'active_support/关注'

module Concerns::Models::Post
  extend ActiveSupport::Concern

  # 'included do' causes the included code to be evaluated in the
  # conext where it is included (post.rb), rather than be 
  # executed in the module's context (blorgh/concerns/models/post).
  included do
    attr_accessible :author_name, :title, :text
    attr_accessor :author_name
    belongs_to :author, class_name: Blorgh.user_class
    has_many :comments

    before_save :set_author

    private
    def set_author
      self.author = User.find_or_create_by_name(author_name)
    end
  end

  def summary
    "#{title}"
  end

  module ClassMethods
    def some_class_method
      'some class method string'
    end
  end
end

当我运行测试/虚拟对象时，我得到了这个错误:未初始化的常量 Blorgh::Concerns

这是我的 blorgh.gemspec:

$:.push File.expand_path("../lib", __FILE__)

# Maintain your gem's version:
require "blorgh/version"


# Describe your gem and declare its dependencies:
Gem::Specification.new do |s|
  s.name        = "blorgh"
  s.version     = Blorgh::VERSION
  s.authors     = ["***"]
  s.email       = ["***"]
  s.homepage    = "***"
  s.summary     = "Engine test."
  s.description = "Description of Blorgh."

  s.files = Dir["{app,config,db,lib}/**/*"] + ["MIT-LICENSE", "Rakefile", "README.rdoc"]
  s.test_files = Dir["test/**/*"]

  s.add_dependency "rails", "~> 3.2.8"
  s.add_dependency "jquery-rails"

  s.add_development_dependency "sqlite3"
end

有人可以帮我弄这个吗？

Answer 1

使用引擎时，您需要跟踪加载顺序，尤其是在更改主应用程序的行为时。假设你的引擎叫做“engine_name”，你应该有这个文件: engine_name/lib/engine_name/engine.rb .这是包含您的关注的一个地方。

Bundler.require

module EngineName
  class Engine < ::Rails::Engine
    require 'engine_name/path/to/concerns/models/post'

    initializer 'engine_name.include_concerns' do
      ActionDispatch::Reloader.to_prepare do
        Blorgh::Post.send(:include, Concerns::Models::Post)
      end
    end

    # Autoload from lib directory
    config.autoload_paths << File.expand_path('../../', __FILE__)

    isolate_namespace EngineName
  end
end

这样可以确保所有内容都正常加载，但在使用 Concerns 时要非常小心，并且可能通过重构 Blorgh::Post 来重新考虑使用依赖注入(inject)来处理不同的配置。