ruby-on-rails - 在执行 ActiveRecord 查询时，如何优先处理具有标记为 true 的属性的记录，然后是 created_at desc ？

Question

我有一堆关于问题的答案。

我想做的是分两步对每个问题的答案进行排序:

1. 如果有一个被接受的答案，先返回那个，然后...
2. 返回其余答案，created_at: :desc

如果#1 不存在，则默认为 2。

这是我试过的，但没有用:

[21] pry(main)> q.answers.order(:accepted, created_at: :desc)
[23] pry(main)> q.answers.order(accepted: true, created_at: :asc).inspect
ArgumentError: Direction "true" is invalid. Valid directions are: [:asc, :desc, :ASC, :DESC, "asc", "desc", "ASC", "DESC"]
from /gems/activerecord-5.0.0.rc1/lib/active_record/relation/query_methods.rb:1164:in `block (2 levels) in validate_order_args'
[24] pry(main)> q.answers.order(accepted: "true", created_at: :asc).inspect
ArgumentError: Direction "true" is invalid. Valid directions are: [:asc, :desc, :ASC, :DESC, "asc", "desc", "ASC", "DESC"]
from gems/activerecord-5.0.0.rc1/lib/active_record/relation/query_methods.rb:1164:in `block (2 levels) in validate_order_args'

我如何实现这一目标？

编辑 1

这是一个带有accepted: true 的答案示例:

[26] pry(main)> q.answers.first
=> #<Answer:0x007f997d7a5a80
 id: 69,
 body:
  "public static Process CreateProcessAsUser(string filename, string args)\r\n {\r\n     var hToken = WindowsIdentity.GetCurrent().Token;\r\n     var hDupedToken = IntPtr.Zero;\r\n\r\n     var pi = new PROCESS_INFORMATION();\r\n     var sa = new SECURITY_ATTRIBUTES();\r\n     sa.Length = Marshal.SizeOf(sa);\r\n\r\n     try\r\n     {\r\n         if (!DuplicateTokenEx(\r\n                 hToken,\r\n                 GENERIC_ALL_ACCESS,\r\n                 ref sa,\r\n                 (int)SECURITY_IMPERSONATION_LEVEL.SecurityIdentification,\r\n                 (int)TOKEN_TYPE.TokenPrimary,\r\n                 ref hDupedToken\r\n             ))\r\n             throw new Win32Exception(Marshal.GetLastWin32Error());\r\n\r\n         var si = new STARTUPINFO();\r\n         si.cb = Marshal.SizeOf(si);\r\n         ",
 user_id: 1547,
 question_id: 47,
 created_at: Wed, 15 Jun 2016 05:20:11 UTC +00:00,
 updated_at: Mon, 20 Jun 2016 22:34:08 UTC +00:00,
 accepted: true,
 language: nil,
 comments_count: nil>

Answer 1

您需要将一个字符串传递给 order 方法:

q.answers.order("accepted = true DESC").order(:created_at)