Rails: Calling one Model from another Model. Why is this not possible?

问题

I have the following Model...

class Room < ActiveRecord::Base
  belongs_to :hotel
  belongs_to :layout
  has_many :visits

  validates :number, presence: true
  validates :rate, presence: true
  validates :smoking, presence: true

  def self.rooms_with_smoking(smoking)
    self.where('smoking = ?', smoking)
  end

  def self.occupied_rooms(from_date, to_date) #24-26
    self.joins(:visits).where('date >= ? and date <= ?', from_date, to_date).uniq
  end

  def self.vacant_rooms(from_date, to_date)
    self.where.not(id: Room.occupied_rooms(from_date, to_date))
  end 

  def self.blahblah(occupancy_count, smoking, from_date, to_date)
    layouts = Layout.layouts_with_occupancy_count_gt(occupancy_count)
    Room.rooms_with_smoking(smoking).vacant_rooms(from_date, to_date).joins(layouts)
  end
end

The blahblah method...

When I attempt to run this from irb I get an error... "unknown class: Layout"

1) Does Room not 'know' about Layout. Can I not use another Model like this? How can I do it.

2) Theory question: Is it better to have one large method definition to obtain some information... or is it better to have a lot of little compartmentalized methods, and use them all in one method to obtain a larger piece of data. For example...

One 'Large' Method:

def self.find_rooms_with(occupancy_count, smoking, from_date, to_date)
    Room.vacant_rooms(from_date, to_date).joins(:layout).where('occupancy_count >= ?', occupancy_count).where('smoking = ?', smoking)
end

By no means large, but everything is re-coded. Doesn't seem like it would follow DRY for long.

Many Little Methods:

  def self.blahblah(occupancy_count, smoking, from_date, to_date)
    layouts = Layout.layouts_with_occupancy_count_gt(occupancy_count)
    Room.rooms_with_smoking(smoking).vacant_rooms(from_date, to_date).joins(layouts)
  end

The second one is easier to code. It utilizes 3 built in method definitions. However, does it have any sort of performance hit over the first one, or is it less desirable?

EDIT: Answering the first two comments below...

When I just type Layout, or ap Layout, I get my entire Layout model.

class Layout < ActiveRecord::Base {
                 :id => :integer,
        :description => :string,
    :occupancy_count => :integer,
         :created_at => :datetime,
         :updated_at => :datetime
}
 => nil

And by irb, yes I mean rails console. Full Layout Model here...

class Layout < ActiveRecord::Base
    has_many :rooms

    validates :description, presence: true
    validates :occupancy_count, presence: true

    def self.layouts_with_occupancy_count(occupancy_count)
        self.where('occupancy_count = ?', occupancy_count)
    end

    def self.layouts_with_occupancy_count_gt(occupancy_count)
        self.where('occupancy_count >= ?', occupancy_count)
    end
end

回答1:

1) It seems you do not declare the Layout class.

The belongs_to class method expects a corresponding ActiveRecord class to be defined. By default it should match the method name (:layout corresponds to Layout).

来源：https://stackoverflow.com/questions/23348610/rails-calling-one-model-from-another-model-why-is-this-not-possible

标签

ruby-on-rails

activerecord

dry