Active Model Serializers：nil的未定义方法`url_for’：NilClass

我在我的应用程序中使用active_model_serializers gem来发送高级json响应。 它实际上工作正常但是因为我已经安装了这个gem，在使用几分钟后，应用程序崩溃，显示上面的错误。

不确定我的代码是否与它有关但不知何故，我还需要发回一些部分代码。 由于它似乎没有得到gem的支持，我做了一个工作：

 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，我可以这样做：

 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，我得到了部分作为JSON属性。 奇怪的是，错误在任何页面上逐渐出现。 删除它的唯一方法是重新启动服务器。 但是，经过几分钟的使用后，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' 

你们中的任何人已经面临过类似的事

编辑：
根据要求，这是我的观点的代码：

 %article#comment-id-1.comment-item.mt = 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.ml-sm.pull-right %i.fa.fa-clock-o = time_ago_in_words activity.created_at .panel-body %div = activity.data[:message] .comment-action.mt-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 

编辑2：

经过多挖掘后，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助手和加载库时，这会导致整个系统不工作。 但是，我该如何解决呢？

Answer 1

好的，我终于找到了解决方法。 问题真的来自上面post中的编辑2点。

要修复它，因为我已经在我的应用程序中使用了rails_config gem（ https://github.com/railsjedi/rails_config ），我已经使用它以便能够直接从我的序列化程序渲染我的部分而不会破坏Rails魔术自动加载。

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，现在它完美无缺。 如果你们有其他方式（更像Rails），我会很想知道它。

谢谢