Rails ActiveRecord scope with multiple conditions

Question

I have a Rails app where I have a Unit model and Status model. Status has_many units and Unit belongs_to Status.

I wrote a scope on Unit to find all of the Units with a specific Status, "In Service" like so:

scope :in_service, lambda { where(status_id: Status.find_by_unit_status("In Service").id)}

This allows me to call Unit.in_service.count to get a count of all Units that are In Service.

But what I really want to do is write a scope that will allow me to scope out all Units with a Status of In Service, At Post, and At Station to get an accurate view of Units since these other two Statuses are considering the Unit to be available.

I'm not sure how I would write something like this. Where the scope contains multiple conditions or data fields.

Can anyone lend a hand?

Update

I tried writing a class method called available like this:

  def self.available
    Unit.where(status_id: Status.find_by_unit_status("In Service").id)
    .where(status_id: Status.find_by_unit_status("At Post").id)
    .where(status_id: Status.find_by_unit_status("At Station").id)
  end

I'm not sure if this method even is what I'm looking for since I want to find Units with each of these statuses. I think what I just wrote might be constraining the method to where the Unit must have all of these statuses.

Peter Brown Peter Brown · Accepted Answer · 2014-08-18T12:22:45

You've got a couple things going on here. First if you want to find all units where the status is one of many, you'll need to pass that as an array like so:

scope :in_service, lambda { where(status_id: Status.where(unit_status: ["In Service", "At Post", "At Station"]).map(&:id))}

Second, in your updated method example, you're chaining a bunch of where clauses together, which will result in each one joined with an AND.

Rails ActiveRecord scope with multiple conditions

1 Answers