活动模型序列化器 returns 默认 JSON 对象

Question

我有一个像这样的活动模型序列化器class

class PostSerializer < ActiveModel::Serializer
 attributes :activities
 def activities
    object.activities.each do |activity|
      post_json(activity) if activity.class.name == 'Post'
      like_json(activity) if activity.class.name == 'PostLike'
      comments_json(activity) if activity.class.name == 'PostComment'
    end
  end

  def post_json(post)
    {
        type: 'share',
        user: post.user_id,
        user_name: post.user.display_name,
        user_image_thumb: post.user.profile.image.thumb.url,
        id: post.id,
        created_at: post.created_at
    } if post
  end

  def like_json(like)
    {
        type: 'like',
        user: like.user_id,
        user_name: like.user.display_name,
        user_image_thumb: like.user.profile.image.thumb.url,
        id: like.id,
        created_at: like.created_at
    } if like
  end

  def comments_json(comment)
    {
        type: 'comment',
        user: comment.user_id,
        user_name: comment.user.display_name,
        user_image_thumb: comment.user.profile.image.thumb.url,
        id: comment.id,
        created_at: comment.created_at,
        content: comment.content
    } if comment
  end
end

但响应总是 returns 默认响应对象并且不包含来自 json 构建器方法的字段。

"activities": [
      {
        "id": 40,
        "user_id": 22,
        "post_id": 8,
        "created_at": "2016-04-22T07:29:26.210Z",
        "updated_at": "2016-04-22T07:29:26.210Z"
      }
]

我该如何纠正这个问题？

Answer 1

将each更改为map:

 def activities
    object.activities.map do |activity|
      post_json(activity) if activity.class.name == 'Post'
      like_json(activity) if activity.class.name == 'PostLike'
      comments_json(activity) if activity.class.name == 'PostComment'
    end
  end

Array#each vs. Array#map