Rails:在请求范围内共享信息

Question

Rails在当前请求范围内共享信息的机制是什么？

那些熟悉Asp.Net的人会知道有一个HttpContext可供请求期间调用的所有实体使用.

Rails中有类似的东西吗？

Answer 1

使用around_filter和Thread.current[]您可以轻松创建请求上下文/范围.请参阅以下示例.

首先加入你的application_controller.rb:

  around_filter :request_context

  def request_context
    begin
      RequestContext.begin_request
      yield
    ensure
      RequestContext.end_request
    end
  end

现在添加以下类 lib/request_context.rb

class RequestContext
  def self.instance
    i = Thread.current[:request_context]
    unless i
      raise "No instance present. In script/rakefiles: use RequestContext.with_scope {}, " +
            "in controller: ensure `around_filter :request_scope` is configured"
    end
    return i
  end

  # Allows the use of this scope from rake/scripts
  # ContextScope.with_scope do |scope|
  #   # do something
  #   ...
  # end
  def self.with_scope
    begin
      begin_request
      yield(instance)
    ensure
      end_request
    end
  end

  def self.begin_request
    raise "request_context already set" if Thread.current[:request_context]
    Thread.current[:request_context] = RequestContext.new
  end

  def self.end_request
    raise "request_context already nil" unless Thread.current[:request_context]
    Thread.current[:request_context] = nil
  end

  # user part, add constructors/getters/setters here

  def initialize
    # you can setup stuff here, be aware that this
    # is being called in _every_ request.
  end
end

这非常简单.您可以将数据存储在RequestContext.instance对象中,该对象将在每次请求后重新创建.