ruby on Rails：通过关联搜索

Question

我有一点理解问题：

我有Channel和Lecturer，其中 a Channel :has_and_belongs_to_many :lecturers。

我想获取 Lecturer.id 为 lect.id 的所有频道。

2.3.0 :235 >   Channel.where(:lecturers => { :id => 2 })
  Channel Load (0.1ms)  SELECT "channels".* FROM "channels"  WHERE "lecturers"."id" = 2
SQLite3::SQLException: no such column: lecturers.id: SELECT "channels".* FROM "channels"  WHERE "lecturers"."id" = 2
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: lecturers.id: SELECT "channels".* FROM "channels"  WHERE "lecturers"."id" = 2

这不起作用，我觉得我不理解核心概念，因为我可以做

2.3.0 :231 > Channel.first.lecturer  
=> #<Lecturer id: 2, name: "Albert Einstein">

我缺少什么？

Answer 1

您需要连接表来执行此查询。请参阅文档

Channel.joins(:lecturer).where(lecturers: {id: lect.id})