ruby on rails - Compare associations on different ActiveRecords without fetching from the DB -

i able compare associated records on activerecords, without fetching database. following comparison, hits db when make comparison

employee1 = employee.find_by(name: 'alice')   debug   employee load (92.0ms)  select "employees".* "employees" "employees"."name" = 'alice' limit 1  employee2 = employee.find_by(name: 'bob')   debug   employee load (92.0ms)  select "employees".* "employees" "employees"."name" = 'bob' limit 1  employee1.manager == employee2.manager   debug   employee load (697.9ms)  select "employees".* "employees" "employees"."id" = $1 order "employees"."id" asc limit 1  [["id", 53]]   debug   employee load (504.1ms)  select "employees".* "employees" "employees"."id" = $1 order "employees"."id" asc limit 1  [["id", 53]]  => true 

i can compare values of foreign columns directly, that's less idiomatic , can difficult refactor later on:

employee1.manager_id == employee2.manager_id  => true 

edit: i've added own answer solution question below

if know you're going needing/using manager employee during operation, can make sure load object when employee loaded, prevent trip database:

employee1 = employee.includes(:manager).find_by(name: 'alice') employee2 = employee.includes(:manager).find_by(name: 'bob') employee1.manager == employee2.manager  => true # database hit not needed... 

that or compare ids, make helper method on employee like

class employee   def same_manager?(other_employee)     other_employee.manager_id == self.manager_id   end end 

at least way it's given name , operation within makes sense in context.