活动模型序列化器：nil:NilClass 的未定义方法“url_for”

我在用着active_model_serializersgem 在我的应用程序中发送高级 json 响应。它实际上工作正常，但由于我安装了该 gem，使用几分钟后，应用程序崩溃，显示上面的错误。

不确定我的代码是否与之相关，但不知何故，我也需要发回一些部分代码。由于宝石似乎不支持它，我做了一个解决办法：

class AppSerializer < ActiveModel::Serializer

  def render_partial_to_json(options = {})
    partial = options[:partial] || nil
    locals  = options[:locals] || nil

    context = Rails.configuration.paths['app/views']
    view    = ActionView::Base.new(context)

    view.class.class_eval do
      include Rails.application.routes.url_helpers
      include ApplicationHelper
    end

    view.render(
      partial: partial,
      locals: locals
    )
  end
end

然后，在我的序列化器中，我可以执行以下操作：

class ActivitySerializer < AppSerializer

  attributes :id, :kind, :data, :created_at, :html

  has_many :comments
  has_one :user

  def id
    ScatterSwap.hash(object.id)
  end

  def html
    render_partial_to_json(
      partial: 'activities/post',
      locals: { activity: object }
    )
  end
end

这段代码工作正常，我得到了我的部分作为 JSON 属性。 奇怪的是，错误逐渐出现在任何页面上。删除它的唯一方法是重新启动服务器。但同样，使用几分钟后，问题又回来了。

这是日志的一部分：

Completed 500 Internal Server Error in 65ms

NoMethodError - undefined method `url_for' for nil:NilClass:
actionpack (4.0.3) lib/action_dispatch/routing/url_for.rb:155:in `url_for'
actionpack (4.0.3) lib/action_view/routing_url_for.rb:83:in `url_for'
turbolinks (2.2.1) lib/turbolinks/xhr_url_for.rb:12:in `url_for_with_xhr_referer'
actionpack (4.0.3) lib/action_dispatch/routing/route_set.rb:234:in `call'
actionpack (4.0.3) lib/action_dispatch/routing/route_set.rb:178:in `call'
actionpack (4.0.3) lib/action_dispatch/routing/route_set.rb:274:in `block (2 levels) in define_url_helper'
app/views/activities/_post.html.haml:2:in `_app_views_activities__post_html_haml__1000109198282705156_2214339020'
actionpack (4.0.3) lib/action_view/template.rb:143:in `block in render'
activesupport (4.0.3) lib/active_support/notifications.rb:161:in `instrument'
actionpack (4.0.3) lib/action_view/template.rb:141:in `render'
actionpack (4.0.3) lib/action_view/renderer/partial_renderer.rb:306:in `render_partial'
actionpack (4.0.3) lib/action_view/renderer/partial_renderer.rb:279:in `block in render'
actionpack (4.0.3) lib/action_view/renderer/abstract_renderer.rb:38:in `block in instrument'
activesupport (4.0.3) lib/active_support/notifications.rb:159:in `block in instrument'
activesupport (4.0.3) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (4.0.3) lib/active_support/notifications.rb:159:in `instrument'
actionpack (4.0.3) lib/action_view/renderer/abstract_renderer.rb:38:in `instrument'
actionpack (4.0.3) lib/action_view/renderer/partial_renderer.rb:278:in `render'
actionpack (4.0.3) lib/action_view/renderer/renderer.rb:47:in `render_partial'
actionpack (4.0.3) lib/action_view/helpers/rendering_helper.rb:27:in `render'
haml (4.1.0.beta.1) lib/haml/helpers/action_view_mods.rb:10:in `block in render_with_haml'
haml (4.1.0.beta.1) lib/haml/helpers.rb:89:in `non_haml'

你们中有人已经面临过类似的事情吗？

EDIT :
根据要求，这是我的观点的代码：

%article#comment-id-1.comment-item.m-t


= link_to profile_url(activity.user), class: "pull-left thumb-sm avatar" do
  = display_picture_for activity.user, resizing_by: "36x36"
  %span.arrow.left
  %section.comment-body.panel.panel-default
    %header.panel-heading.bg-white
      = link_to profile_url(activity.user) do
        = activity.user.fullname
      %span.text-muted.m-l-sm.pull-right
        %i.fa.fa-clock-o
        = time_ago_in_words activity.created_at
    .panel-body
      %div
        = activity.data[:message]
      .comment-action.m-t-sm
        %a.btn.btn-default.btn-xs.active{"data-toggle" => "class", href: "#"}
          %i.fa.fa-star-o.text-muted.text
          %i.fa.fa-star.text-danger.text-active
          Like
        %a.btn.btn-default.btn-xs{href: "#comment-form"}
          %i.fa.fa-mail-reply.text-muted
          Reply

EDIT 2 :

经过更多挖掘后，我发现这段代码：

class AppSerializer < ActiveModel::Serializer

  def render_partial_to_json(options = {})
    partial = options[:partial] || nil
    locals  = options[:locals] || nil

    context = Rails.configuration.paths['app/views']
    view    = ActionView::Base.new(context)

    view.class.class_eval do
      include Rails.application.routes.url_helpers
      include ApplicationHelper
    end

    view.render(
      partial: partial,
      locals: locals
    )
  end
end

当调用覆盖Rails助手并加载库时，这会导致整个系统无法工作。然而，我该如何解决它呢？

好吧，我终于找到了解决办法。问题确实出在我身上edit 2上面帖子里的点。

要修复它，因为我已经在使用rails_config gem (https://github.com/railsjedi/rails_config https://github.com/railsjedi/rails_config）在我的应用程序中，我使用它是为了能够直接从序列化器渲染我的部分内容，而不会破坏 Rails 神奇的自动加载。

首先，我将上下文设置为配置（设置）：

# application_controller
class ApplicationController < ActionController::Base
  before_filter :set_context_for_serializer

  def set_context_for_serializer
    Settings.context = self
  end
end

然后，在我的序列化器中，我需要做的就是：

class ApplicationSerializer < ActiveModel::Serializer
  def render_partial_to_json(options = {})
    partial = options[:partial] || nil
    locals  = options[:locals] || nil

    Settings.context.render_to_string(
      partial: partial,
      layout: false,
      formats: :html,
      locals: locals
    )
  end
end

class ActivitySerializer < ApplicationSerializer
  attributes :id, :kind, :data, :created_at, :html

  def html
    render_partial_to_json(
      partial: 'activities/post',
      locals: { activity: object }
    )
  end
end

就是这样，现在它可以完美运行了。如果你们有其他方法（更像Rails）来做到这一点，我会很想知道。

Thanks