Rails Scope with Multiple Joins and Parameters

Question

I've tried solutions from other questions but am still having trouble. I also can't seem to find if there is a good way to debug the query, so I've only been able to use trial and error.

I am creating a scope on Service .

My Service has an optional belongs_to relationship with `Affiliate:

class Service < ApplicationRecord
    belongs_to :affiliate,  optional: true
end 

Service also has a lonlat column:

create_table "services", force: :cascade do |t|
    t.bigint "affiliate_id"
    t.geography "lonlat", limit: {:srid=>4326, :type=>"st_point", :geographic=>true}
    t.index ["affiliate_id"], name: "index_services_on_affiliate_id"
    t.index ["lonlat"], name: "index_services_on_lonlat", using: :gist
  end

My Affiliate has a belongs_to relationship with AffiliatePlan :

class Affiliate < ApplicationRecord
    belongs_to :affiliate_plan
end 

My AffiliatePlan has a radius_miles column:

create_table "affiliate_plans", force: :cascade do |t|
    t.decimal "radius_miles"
end 

Given a longitude and a latitude, my goal is to find all services that are within their AffiliatePlan 's radius from the coordinates.

Here's my latest attempt in my Service class:

scope :within_with_cat, -> (latitude, longitude){ 
    joins(:services, :affiliates, :affiliate_plans)
        .where("ST_Distance(service.lonlat, 'POINT(:lo :la)') < (affiliate_plan.radius_miles * 1609.34)", lo: longitude, la: latitude)
}

I have tried both the singular and plural for service.lonlat . I always get an empty relation back. I have tried without the join tables using a set value for the miles and have gotten back services, so it seems the geospatial side of things is working.

Answer 1

Here's how I was able to get it working:

scope :within_with_cat, -> (latitude, longitude){ 
    joins(affiliate: [ :affiliate_plan])
        .where(['(ST_Distance(lonlat, \'POINT(%f %f)\') < (affiliate_plans.radius_miles * 1609.34))', longitude, latitude])
}

One of my biggest areas of confusion was that I didn't need to join the table for the model the scope is in.

I discovered that if I called Service.within_with_cat(lat, lon).any? I would receive the error messages needed for debugging. When I called Service.within_with_cat(lat, lon) I would only receive a relation with no errors.