Redmine-Jobs/app/models/job.rb

class Job < ActiveRecord::Base
  validates :starts_on,
            :ends_on,
            :name,
            presence: true

  belongs_to :project

  scope :project, ->(project) { where(project_id: project.id) }

  def total_time_logged
    TimeEntry.where(job_id: id)
             .sum(:hours)
  end

  def total_time_logged_for(activity)
    TimeEntry.where(job_id: id, activity_id: activity.id)
             .sum(:hours)
  end
end