如何在引擎中使用引擎中的中间件

Question

由于不同的 gem 在我的系统中如何交互，我将一个引擎安装到 rails 应用程序上。我最近开始研究一个提供一些中间件功能的新 gem。

有点像这样：

BaseApp
\
  Engine
  \
   NewMiddlewareEngine

# BaseApp/Gemfile
gem 'Engine'

# Engine/Gemfile
gem 'NewMiddlewareEngine'

# rake middleware output:
user@laptop[BaseApp]$ bundle exec rake middleware
use Rack::Sendfile
use ActionDispatch::Static
use Rack::Lock
use #<ActiveSupport::Cache::Strategy::LocalCache::Middleware:0x6ebf30e1>
use Rack::Runtime
use Rack::MethodOverride
use ActionDispatch::RequestId
use Rails::Rack::Logger
use ActionDispatch::ShowExceptions
use ActionDispatch::DebugExceptions
use ActionDispatch::RemoteIp
use ActionDispatch::Reloader
use ActionDispatch::Callbacks
use ActiveRecord::Migration::CheckPending
use ActiveRecord::ConnectionAdapters::ConnectionManagement
use ActiveRecord::QueryCache
use ActionDispatch::Cookies
use ActionDispatch::Session::CookieStore
use ActionDispatch::Flash
use CatchJsonParseErrors
use ActionDispatch::ParamsParser
use Rack::Head
use Rack::ConditionalGet
use Rack::ETag
run BaseApp::Application.routes

但是，我似乎无法让 NewMiddlewareEngine 出现在中间件中。我已经测试过安装这个：

BaseApp
\
 NewMiddlewareEngine

# BaseApp/Gemfile
gem 'NewMiddlewareEngine'

# rake middleware output:
user@laptop[BaseApp]$ bundle exec rake middleware
use Rack::Sendfile
use ActionDispatch::Static
use Rack::Lock
use #<ActiveSupport::Cache::Strategy::LocalCache::Middleware:0x2f9795d8>
use Rack::Runtime
use Rack::MethodOverride
use ActionDispatch::RequestId
use Rails::Rack::Logger
use ActionDispatch::ShowExceptions
use ActionDispatch::DebugExceptions
use ActionDispatch::RemoteIp
use ActionDispatch::Reloader
use ActionDispatch::Callbacks
use ActiveRecord::Migration::CheckPending
use ActiveRecord::ConnectionAdapters::ConnectionManagement
use ActiveRecord::QueryCache
use ActionDispatch::Cookies
use ActionDispatch::Session::CookieStore
use ActionDispatch::Flash
use CatchJsonParseErrors
use ActionDispatch::ParamsParser
use Rack::Head
use Rack::ConditionalGet
use Rack::ETag
use NewMiddlewareEngine    # Notice it mounts fine on it's own
run BaseApp::Application.routes    

还有：

BaseApp
\
 Engine

# BaseApp/Gemfile
gem 'Engine'

# rake middleware output:
user@laptop[BaseApp]$ bundle exec rake middleware
use Rack::Sendfile
use ActionDispatch::Static
use Rack::Lock
use #<ActiveSupport::Cache::Strategy::LocalCache::Middleware:0x6ebf30e1>
use Rack::Runtime
use Rack::MethodOverride
use ActionDispatch::RequestId
use Rails::Rack::Logger
use ActionDispatch::ShowExceptions
use ActionDispatch::DebugExceptions
use ActionDispatch::RemoteIp
use ActionDispatch::Reloader
use ActionDispatch::Callbacks
use ActiveRecord::Migration::CheckPending
use ActiveRecord::ConnectionAdapters::ConnectionManagement
use ActiveRecord::QueryCache
use ActionDispatch::Cookies
use ActionDispatch::Session::CookieStore
use ActionDispatch::Flash
use CatchJsonParseErrors
use ActionDispatch::ParamsParser
use Rack::Head
use Rack::ConditionalGet
use Rack::ETag
run BaseApp::Application.routes

两者都可以正常工作。问题是当我尝试“通过”引擎安装 NewMiddlewareEngine 时。

有人知道如何配置这样的东西吗？

这是 MyMiddlewareEngine 安装：

module MyMiddlewareEngine
  class Railtie < Rails::Railtie
    initializer "add_my_middleware_engine_route_middleware" do |app|
      app.middleware.use 'MyMiddlewareEngine'
    end
  end
end

Answer 1

来自Rails::Engine Edge API 文档：

 class MyEngine < Rails::Engine
   # Add a load path for this specific Engine
   config.autoload_paths << File.expand_path("../lib/some/path", __FILE__)

   initializer "my_engine.add_middleware" do |app|
     app.middleware.use MyEngine::Middleware
   end
 end

我倾向于将 Rails 中间件配置为在应用程序级别而不是在引擎中运行（作为职责分离）。我使用这种方法将身份验证与已安装的 rails 应用程序分开（请参阅example）。这个配置在application.rb:

 module MyApp
   class Application < Rails::Application
     ..
     config.middleware.use NewMiddlewareEngine

您在运行 rails 控制台时是否看到任何异常？您是否尝试过使用上述常量名称而不是 String？