How to access certain database tables in Rails controller?

Question

I am using Rails as a JSON API. My database has the following structure: the City model has_many Users, which in turn has_many Businesses.

When I send a GET request to businesses#index, I want Rails to return all the businesses in a given city, not just for a given user. What's the best way to do this?

I've already tried the given code below as a first pass, which is returning an internal server error (500).

def index
    @city = City.find(params[:city_id])

    @users = @city.users
    @businesses = @users.businesses

    render json: @businesses
end

Answer 1

Can you try this? Because of the @user is an array. so the error will occuring.

 # city.rb class City < ApplicationRecord has_many :users end #user.rb class User < ApplicationRecord belongs_to :invoice has_many :businesses end #business.rb class Business < ApplicationRecord belongs_to :user end # your controller def get_business @city = City.find(params[:id]) @business = @city.users.includes(:business) render json: @business end 

Answer 2

Add a new relationship to your City model: has_many businesses, through: users

Then when you have a specific city you can get all businesses: @city.businesses

Answer 3

You might also want to try starting with the Business model to make the query.

Business.joins(user: :city).where(cities: { id: params[:city_id] })

joins uses the association names

where uses the table names