How to have multiple conditions in a named scope?

问题

I have a User model. I can check whether a User is an admin by doing a_user.try(:admin?).

I'd like to define a named scope that gets all Users updated within the last X minutes who are not admins. So far I have:

scope :recent, lambda { { :conditions => ['updated_at > ?', 5.minutes.ago] } }

This successfully gets all Users updated within the last 5 minutes, but how do I incorporate the admin check? I don't know how to call try() on an instance of a User inside the scope...

回答1:

if admin column in users table is a boolean,

scope :recent, lambda { :conditions => ['updated_at > ? AND admin != ?', 5.minutes.ago, true] }

回答2:

Just another possibility, usable in Rails 4,

scope :recent, -> { where('updated_at > ?', 5.minutes.ago }
# If you were using rolify, you could do this
scope :non_admin, -> { without_role :admin }
# given the OP question,
scope :non_admin, -> { where(admin: false) }
scope :non_admin_recent, -> { non_admin.recent }

This is just another possible format and taking in account the possibility of using Rolify gem.

回答3:

Instead of using lambda, I find it cleaner to use class methods.

def self.recent
  where('updated_at > ?', 5.minutes.ago)
end

def self.admin
  where(admin: true)
end

def self.recent_and_admin
  recent.admin # or where('updated_at > ?', 5.minutes.ago).where(admin: true)
end

来源：https://stackoverflow.com/questions/14623668/how-to-have-multiple-conditions-in-a-named-scope