Why does my ActiveRecord scope with `merge` return an array?

问题

I have a scope on my Contract model that uses merge and returns an array, not an ActiveRecord::Relation as I would like.

Yes, I've seen it said that "It is an ActiveRecord::Relation, but Rails is intentionally lying to you". But in this case:

The scope uses merge
it only works if it's the last scope in the chain
The object it returns says it's of class Array
The object it returns has nothing about ActiveRecord in its ancestors
Calling ActiveRecord::Relation methods like scoped on the return value raises raises NoMethodError: undefined method 'scoped' for []:Array.

The scope is on Contract and looks something like

scope :hourly, scoped.merge(Division.find_by_name!('Hourly').contracts)

Why is this returning an array? Can I get it to return an ActiveRecord::Relation?

回答1:

Ref comments above. I gave this a go with a dummy relationship which I expect you have with Division and Contract.

# app/models/contract.rb

scope :hourly,
  select: 'distinct contracts.*',
  joins: :divisions,
  conditions: {
    "divisions.name" => 'Hourly'
  },
  order: :id

contracts = Contracts.hourly
# => [#<Contract id: 1>, #<Contract id: 2>]

contracts.class
# => #<ActiveRecord::Relation>

contracts.scoped.class
# => #<ActiveRecord::Relation>

contracts.arel
# => #<Arel::SelectManager:0x007fab629f7e90>

contracts.to_a
# => [#<Contract id: 1>, #<Contract id: 2>]

contracts.to_sql
# => SELECT distinct contracts.* FROM `contracts` INNER JOIN `divisions` ON `divisions`.`contract_id` = `contracts`.`id` WHERE `divisions`.`name` = 'Hourly' ORDER BY id

Let me know if this is what you were looking for...

来源：https://stackoverflow.com/questions/16927437/why-does-my-activerecord-scope-with-merge-return-an-array

标签

ruby

rails-activerecord