Question

虽然视图包含（我相信）是显示提要的正确UNLESS语句，但当用户没有关注任何人时，来自micropost.rb模型的SQL方法似乎无效。此错误在部署环境（例如Heroku）中是透明的 - 这是从应用程序生成500响应的日志片段：

Started GET "/" for 71.180.163.2 at Mon Jan 31 12:10:07 -0800 2011
  Processing by PagesController#home as HTML
Completed   in 9ms


ActiveRecord::StatementInvalid (PGError: ERROR:  syntax error at or near ")"
LINE 1: ...* FROM       "microposts"  WHERE     (user_id IN () OR user_...
                                                            ^

: SELECT     "microposts".* FROM       "microposts"  WHERE     (user_id IN () OR user_id = 1) ORDER BY  microposts.created_at DESC LIMIT 30 OFFSET 0):

app / controllers / pages_controller.rb：6：在'home'

问题是，如何在没有黑客修复的情况下解决此问题，例如在User.create上自动关注用户！

它有帮助，这个问题的要点是：https://gist.github.com/804754

Answer 1

删除微博模型中的初始self.from_users_followed_by方法，让私有的self.followed_by（用户）方法独立，似乎解决了这个问题。所有测试都通过了。

来自models / micropost.rb

class Micropost < ActiveRecord::Base
attr_accessible :content

belongs_to :user

validates :content, :presence => true, :length => { :maximum => 140 }
validates :user_id, :presence => true

default_scope :order => 'microposts.created_at DESC'

#Return microposts from the users being followed by the given user--
scope :from_users_followed_by, lambda { |user| followed_by(user) }
# 
# def self.from_users_followed_by(user)
#   followed_ids = user.following.map(&:id).join(", ")
#   where("user_id IN (#{followed_ids}) OR user_id = ?", user)
# end

private

#Return an SQL condition for users followed by the given user.
#We include the user's own ID as well--
def self.followed_by(user)
  followed_ids = %(SELECT followed_id FROM relationships
                   WHERE follower_id = :user_id)
  where("user_id IN (#{followed_ids}) OR user_id = :user_id",
        :user_id => user)
end
end

Answer 2

无需像在from_users_followed_by方法中那样手动构建查询字符串。我会做类似的事情：

def self.from_users_followed_by(user)
  followed_ids = user.following.map(&:id) + user.id
  where(:user_id => followed_ids)
end

RubyTutorial.org：无效的SQL语句在页面#home上生成500响应

2 个答案: