Question

我有一个班级模特，一个学生模型和一个考勤模型。学生可以参加考勤以提高绩效。

我想显示班级中所有学生的数量，现在学生的数量，缺席学生的数量和出勤率。我是Mongodb的新手，我将不胜感激任何帮助。谢谢你的时间。

class Klass
  include Mongoid::Document
  include Mongoid::Timestamps

  has_and_belongs_to_many :students

  field :name, type: String
end

class Student
  include Mongoid::Document
  include Mongoid::Timestamps

  has_and_belongs_to_many :klasses
  embeds_many :attendances

  field :name, type: String
end

class Attendance
  include Mongoid::Document
  include Mongoid::Timestamps

  embedded_in :student

  field :status, type: Integer # 1 = Present, 2 = Absent
  field :klass_id, type: BSON::ObjectId
end

Answer 1

你可以试试这些：

@class = Klass.where(name: 'something').first

@total_students = @class.students.count

@present_students = @class.students.where('attendances.status' => '1').count

@absent_students = @class.students.where('attendances.status' => '2').count

@p_s_today = @class.students.where('attendances.status' => '1', 'attendances.created_at' => {'$gte' => Date.today} ).count

@a_s_today = @class.students.where('attendances.status' => '2', 'attendances.created_at' => {'$gte' => Date.today} ).count

Answer 2

我已经通过遵循技术解决了我的问题。

@students_present_today = @class.students.where({ attendances: { '$elemMatch' => {status: 1, :created_at.gte => Date.today} } }).count
@students_absent_today = @class.students.where({ attendances: { '$elemMatch' => {status: 2, :created_at.gte => Date.today} } }).count

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