通过has_many找到Rails:through

Question

我正在寻找一种方法来查询基于has_many通过关联的子项的模型.

我有3个型号:

class Conversation < ActiveRecord::Base
   has_many :conversations_participants
   has_many :participants, through: :conversations_participants
end

class ConversationsParticipant < ActiveRecord::Base
   belongs_to :conversation
   belongs_to :participant, class_name: 'User'
end

class User < ActiveRecord::Base
   has_many :conversations_participants
   has_many :conversations, through: :conversations_participants
end

我需要找到参与者匹配一组id的对话.

这就是我现在所拥有的(不工作):

Conversation.includes(:participants).where(participants: params[:participants])

Answer 1

听起来你只想要对话,如果可以的话joins.

Conversation.joins(:participants).where(:users => { :id => params[:participants] } )

否则,如果您想加载参与者,请使用 includes

Conversation.includes(:participants).where(:users => { :id => params[:participants] } )