Question

我的控制器中有此代码，该代码应为我提供特定类别中的最新更新帖子。

def set_subcategory_meta_data(category_param)
  post = Post.where("category = ?", category_param).order("updated_at").last
  @last_post_title = post.title
  @last_post_user_name = 'JohnDoe20181827'
  @last_post_update_time = '(25.08.2018, 16:08)'
  @post_count = Post.where("category = ?", category_param).count
  @comment_count = 999
  @last_post_path = user_path(User.first)
  @last_post_user_path = user_path(User.last)
end

它不起作用，给了我nil：class的帖子。但是它在命令行的Rails控制台中工作得很好。

我不知道我在这里做错了什么...

irb(main):010:0> post.title="hey he euy"
=> "hey he euy"
irb(main):011:0> post.save
   (0.0ms)  BEGIN
  User Load (2.0ms)  SELECT  "users".* FROM "users" WHERE "users"."id" = $1 LIMIT $2  [["id", 64], ["LIMIT", 1]]
  Post Exists (0.0ms)  SELECT  1 AS one FROM "posts" WHERE LOWER("posts"."title") = LOWER($1) AND "posts"."id" != $2 LIMIT $3  [["title", "hey he euy"], ["id", 1], ["LIMIT", 1]]
  Post Update (1.0ms)  UPDATE "posts" SET "title" = $1, "updated_at" = $2 WHERE "posts"."id" = $3  [["title", "hey he euy"], ["updated_at", "2018-09-11 15:49:43.758079"], ["id", 1]]
   (1.0ms)  COMMIT
=> true
irb(main):012:0> Post.where("category = ?", "ruby-on-rails/developers").order("updated_at").last.title
  Post Load (0.0ms)  SELECT  "posts".* FROM "posts" WHERE (category = 'ruby-on-rails/developers') ORDER BY updated_at DESC LIMIT $1  [["LIMIT", 1]]
=> "hey he euy"

Answer 1

它不起作用，给了我nil：class的帖子。但是它只是有效在命令行的Rails控制台中可以正常运行。

您的方法存在的问题是category_param为 nil 或没有记录与特定的category_param一起导致 nil post 。确保category_param为 nil 且不存在现有类别，以便查询将返回记录。

OR

您可以重写此行

@last_post_title = post.title

为

@last_post_title = post.title if post

避免错误

数据库查询在控制台中没有错误，但在Controller类中没有错误

1 个答案: