Rails 4 query, scoped by condition from has many through attributes - ruby-on-rails

Question

The question is : "given a company, how should I build the query that returns all events created by all employees during their respective employments periods ?"
Ex:
#company = Company.create
# Welcome John
#john = User.create
#event_a = #john.events.create date: Date.new(2013,6,1)
#event_b = #john.events.create date: Date.new(2014,1,1)
#company.employments.create user:#john, since: Date.new(2013,12,20)
# Welcome Jack
#jack = User.create
#event_c = #jack.events.create date: Date.new(2012,1,1)
#event_d = #jack.events.create date: Date.new(2013,1,1)
#company.employments.create user:#jack,
since: Date.new(2011,12,20), till: Date.new(2012,12,31)
#company.events
=> [#event_b, #event_c]
# #event_a is not returned because it was created prior to John's hiring
# #event_d is not returned because it was created after Jack's departure
I came up with a solution but I would like to know if there are any ways to improve it.
class Event
belongs_to :user
# attributes
# date: datetime
# …
end
class Employment
belongs_to :user
belongs_to :event
# attributes
# since: date
# till: date
# …
end
class Company
has_many :employments
def events
Event.where employments.map do |e|
if e.since && e.till
"(user_id = '#{e.user_id}' AND date BETWEEN '#{e.since}' AND '#{e.till}')"
elsif !e.since.nil?
"(user_id = '#{e.user_id}' AND date > '#{e.since}')"
else
"(user_id = '#{e.user_id}')"
end
end.join(' OR ')
end
end
Do you see any other way to do that ?

Answer 1

Events.joins(user: :employments).where(company_id: id)I believe you could use something like this:
def events
Event.where employments.map do |e|
user=User.find(e.user_id)
since = e.since
till = e.till || Date.parse('3100-12-31') # a day in the distant future if nil
user.events.where('(date is null) or (date > ? and date < ?)', since, till)
end
end
2nd try, after using the appropriate joins to connect Event and Employment model, you can use the final where clause to implement your filter.
The full method, after you've added the right set of joins and filters (thanks), is as follows.
def events
Events.joins(user: :employments).where(company_id: id). # <-This comes from the author, not me.
where('employments.since is null OR
(employments.since < events.date AND employments.till is null) OR
(employments.since < events.date AND employments.till > events.date)')
end

Answer 2

how can I query all events created by all employees during their
employment for a given company
You may wish to use an ActiveRecord Association Extension, which basically appends a new method to your association, allowing you to define filtration or some other specifications:
#app/models/company.rb
Class Company < ActiveRecord::Base
has_many :employments
has_many :events do
def by_date(since, till)
... logic here
end
end
end
This will allow you to call:
#app/controllers/events_controller.rb
Class EventsController < ApplicationController
def action
company = Company.find params[:id]
#events = company.events.by_date("01-01-2014", "04-01-2014")
end
end
If you let me know in the comments, I'll have a go at populating the method for you