序列化rails中自定义jsonapi资源的模型

Question

当我使用 jsonapi-resources 向我的 rails 项目中的自定义路由发出请求时，我得到：

NoMethodError: undefined method `each_key' for nil:NilClass

  0) ArticlesController when requesting latest_article succeeds
     Failure/Error: serializer.serialize_to_hash(Article.latest)

     NoMethodError:
       undefined method `each_key' for nil:NilClass
     # /Users/me/.rbenv/versions/2.7.3/gemsets/blog-api/bundler/gems/jsonapi-resources-bf4b4cd7d79d/lib/jsonapi/resource_set.rb:37:in `populate!'
     # /Users/me/.rbenv/versions/2.7.3/gemsets/blog-api/bundler/gems/jsonapi-resources-bf4b4cd7d79d/lib/jsonapi/resource_serializer.rb:49:in `serialize_to_hash'
     # ./app/controllers/articles_controller.rb:4:in `latest'
     # /Users/me/.rbenv/versions/2.7.3/gemsets/blog-api/gems/actiontext-6.1.4.4/lib/action_text/rendering.rb:20:in `with_renderer'
     # /Users/me/.rbenv/versions/2.7.3/gemsets/blog-api/gems/actiontext-6.1.4.4/lib/action_text/engine.rb:59:in `block (4 levels) in <class:Engine>'
     # /Users/me/.rbenv/versions/2.7.3/gemsets/blog-api/gems/rack-2.2.3/lib/rack/etag.rb:27:in `call'
     # /Users/me/.rbenv/versions/2.7.3/gemsets/blog-api/gems/rack-2.2.3/lib/rack/conditional_get.rb:27:in `call'
     # /Users/me/.rbenv/versions/2.7.3/gemsets/blog-api/gems/rack-2.2.3/lib/rack/head.rb:12:in `call'
     # /Users/me/.rbenv/versions/2.7.3/gemsets/blog-api/gems/railties-6.1.4.4/lib/rails/rack/logger.rb:37:in `call_app'
     # /Users/me/.rbenv/versions/2.7.3/gemsets/blog-api/gems/railties-6.1.4.4/lib/rails/rack/logger.rb:26:in `block in call'
     # /Users/me/.rbenv/versions/2.7.3/gemsets/blog-api/gems/railties-6.1.4.4/lib/rails/rack/logger.rb:26:in `call'
     # /Users/me/.rbenv/versions/2.7.3/gemsets/blog-api/gems/rack-2.2.3/lib/rack/runtime.rb:22:in `call'
     # /Users/me/.rbenv/versions/2.7.3/gemsets/blog-api/gems/rack-2.2.3/lib/rack/sendfile.rb:110:in `call'
     # /Users/me/.rbenv/versions/2.7.3/gemsets/blog-api/gems/railties-6.1.4.4/lib/rails/engine.rb:539:in `call'
     # /Users/me/.rbenv/versions/2.7.3/gemsets/blog-api/gems/rack-test-1.1.0/lib/rack/mock_session.rb:29:in `request'
     # /Users/me/.rbenv/versions/2.7.3/gemsets/blog-api/gems/rack-test-1.1.0/lib/rack/test.rb:266:in `process_request'
     # /Users/me/.rbenv/versions/2.7.3/gemsets/blog-api/gems/rack-test-1.1.0/lib/rack/test.rb:119:in `request'
     # ./spec/requests/articles_controller_spec.rb:22:in `block (3 levels) in <top (required)>'

我在这里做错了什么？更重要的是，我该如何解决？

出于这个问题的目的，我有一个带有 Article 和 Comment 模型的 Rails 项目。我使用jsonapi-resources 来生成所有的 CRUD 路由：

Rails.application.routes.draw do
  jsonapi_resources :articles do
    collection do
      get :latest
    end
  end
  jsonapi_resources :comments
end

我添加了一个自定义的articles/latest 路由来返回最新的文章。我正在使用JSONAPI::ResourceSerializer 来序列化Article 之后的the serializer documentation 对象

class ArticlesController < JSONAPI::ResourceController
  def latest
    serializer = JSONAPI::ResourceSerializer.new(ArticleResource)
    serializer.serialize_to_hash(Article.latest)
  end
end

我写了一个规范来复制错误：

describe 'ArticlesController' do
  let!(:articles) { create_list(:article, 10)}

  context 'when requesting articles' do
    it 'succeeds' do
      get articles_path
      expect(response).to have_http_status(:ok)
    end
  end

  context 'when requesting latest_article' do
    it 'succeeds' do
      get latest_articles_path
      expect(response).to have_http_status(:ok)
    end
  end
end

对于已经做到这一点的任何人，我有a complete MCVE project on my GitHub.

从调试中可以看出，serializer.serialize_to_hash 创建了一个带有resource_set = JSONAPI::ResourceSet.new(source, include_related, options) 的JSONAPI::ResourceSet。

这里是JSONAPI::initialize：

    def initialize(source, include_related = nil, options = nil)
      @populated = false
      tree = if source.is_a?(JSONAPI::ResourceTree)
               source
             elsif source.class < JSONAPI::BasicResource
               JSONAPI::PrimaryResourceTree.new(resource: source, include_related: include_related, options: options)
             elsif source.is_a?(Array)
               JSONAPI::PrimaryResourceTree.new(resources: source, include_related: include_related, options: options)
             end

      if tree
        @resource_klasses = flatten_resource_tree(tree)
      end
    end

我不了解if...elsif 链中的情况，但没有一个条件对我来说是正确的，所以tree 是nil，所以@resource_classes 也是nil。

在此之后，serialize_to_hash 调用 resource_set.populate!，后者又调用 @resource_klasses.each_key，但 @resource_classes 是 nil。

我目前的假设是我做错了导致ResourceSet.initialize 跳过初始化@resource_klasses。但我不知道如何解决它。有什么想法或建议吗？

Answer 1

这里的问题是serialize_to_hash 不接受ActiveRecord 对象作为参数。相反，我需要向它传递一个资源，例如：

    serializer.serialize_to_hash(ArticleResource.new(Article.latest, {}))

我觉得jsonapi-resources 可以在这里给出一个有意义的错误信息，而不是用NoMethodError 炸毁。