如何验证关联的模型？

Question

Is my first time building a custom validation , since trying to the regular ORM validations did not work. I have a model called AdGroup which belongs to another model called Car. I want to send prevent that a user creates a new Ad Group if they have not selected a car. Also the Car is a file.

class AdGroup < ActiveRecord::Base
  belongs_to :car
  validate :validate_car_id

  def validate_car_id
    car = Car.find_by(id: params[:id])
    if car.nil?
      errors.add(:car, "Select a car image")
    end
  end
end

class Car < ActiveRecord::Base
  validates :make, :model, :year, presence: true                  
  validates :file, presence: true
  belongs_to :make
  has_many :ad_groups

  ...
end

Is an image that I am trying to select .

Answer 1

Your Ad Group model needs to be associated with the Car model. AdGroup models should have belongs_to :car line and the Car model needs has_many :ad_groups .

To validate associated models you could use ActiveRecord's validates_associated . Be sure to read the docs by the link for gotchas.

class AdGroup < ActiveRecord::Base
  belongs_to :car

  validates :car, presence: true
  validates_associated :car
end

When using validates_associated you don't have to do custom validation.