personal-course/app/models/course_assignment.rb

class CourseAssignment
	include Mongoid::Document
	include Mongoid::Timestamps
    include Slug
	field :name, as: :slug_title, type: String, localize: true, default: ""
	field :deadline, type: DateTime, default: DateTime.now
    field :assign_date, type: DateTime, default: DateTime.now
    field :detail, type: String, localize: true, default: ""
    has_many :course_attachments, :dependent => :destroy, :autosave => true
    accepts_nested_attributes_for :course_attachments, :allow_destroy => true
	belongs_to :course
    scope :enabled_for_student, ->{where(:assign_date.lte=>DateTime.now)}
    def display_attachments
        self.course_attachments.map{|f|
            next if f.file.file.nil?
            title = (f.title.blank? ? f.file.file.original_filename : f.title)
            "<a href=\"#{f.file.url}\" title=\"#{title}\">#{title}</a>"
        }.join("<br>").html_safe
    end
    def display_deadline
        self.deadline.strftime("%Y-%m-%d %H:%M") rescue ""
    end
    def display_assign_date
        self.assign_date.strftime("%Y-%m-%d %H:%M") rescue ""
    end
    def deliver_count
        StudentAssignment.where(:course_assignment_id => self.id,:member_profile_id.ne=>nil).count rescue 0
    end
end