How to create a scope to order cities name?

问题

I have two models/tables: Services and City

Service model:

belongs_to :origin_city, class_name: 'City'
belongs_to :destiny_city, class_name: 'City'

How do I create a scope to order cities name?

I'm trying something like that:

scope :by_city_name, -> { joins(:city).order("cities.name asc") }

But I just want to order the service origin city in one scope. And service destiny city in another scope.

回答1:

So you should join only origin_city:

scope :by_origin_city_name, -> { joins(:origin_city).order('cities.name asc') }

来源：https://stackoverflow.com/questions/27816930/how-to-create-a-scope-to-order-cities-name