如何通过has_many查询关联：

Question

I have a Rails app with a has_many :through association between User.rb and Practice.rb, with PracticeListing.rb as a join model.

User.rb

  has_many :practice_listings
  has_many :practices, through: :practice_listings

Practice.rb

has_many :practice_listings
has_many :users, through: :practice_listings

PracticeListing.rb

  belongs_to :practice
  belongs_to :user

In one of the controllers, I call this scope method on user.rb , passing in the practice_id

 scope :lawyers_by_practice, lambda {|practice_id|
  joins(:practices).
  where( users: {practice_id: practice_id},
         users: {lawyer: true},)

  }

the query from the logs which shows that practice_id is not being used

User Load (1.1ms)  SELECT "users".* FROM "users" INNER JOIN "practice_listings" ON "practice_listings"."user_id" = "users"."id" INNER JOIN "practices" ON "practices"."id" = "practice_listings"."practice_id" WHERE "users"."lawyer" = 't' AND (reputation IS NOT NULL) ORDER BY reputation DESC

Can you explain how I should have written that scope method to get the desired results?

With the current model set up, I could do user.practice_ids for a certain user and get an array of the practice_ids ['2','4']

Update

I tried this way (without joining :practices) in the hopes that the query would select only the users with the relevant practice_id, but it returned every user in the db, even those who didn't have a practice

 scope :lawyers_by_practice, lambda {|practice_id|
  where( users: {practice_id: practice_id},
         users: {lawyer: true},)

  }

I also tried this way (by joining :practice_listings instead) but it returned entries for every practice_listing, again ignoring the fact that I only wanted use who had a certain practice id

scope :lawyers_by_practice, lambda {|practice_id|
    joins(:practice_listings).
  where( users: {practice_id: practice_id},
         users: {lawyer: true},)

  }

Answer 1

User doesn't have a practice_id , only PracticeListing has.

scope :lawyers_by_practice, lambda {|practice_id|
  joins(:practices,:practice_listings).
  where( practice_listings: {practice_id: practice_id},
     users: {lawyer: true},)

  }