Javascript 如何在MongoDB/Mongoose中使用一对多关系连接/填充3个表？

我的模式如下所示：

Teacher.js

const teacherSchema = new mongoose.Schema(
  {
    name: {
      type: String,
      required: true,
      unique: true,
    },
  },
  {
    timestamps: true,
  }
);

teacherSchema.virtual('students', {
  ref: 'Student',
  localField: '_id',
  foreignField: 'teacher',
  justOne: false
})

const Teacher = mongoose.model('Teacher', teacherSchema);

const studentSchema = new mongoose.Schema(
  {
    name: {
      type: String,
      required: true,
    },
    teacher: {
      type: mongoose.Schema.Types.ObjectId,
      ref: 'Teacher',
      required: true,
    },
  },
  {
    timestamps: true,
  }
);

menuItemSchema.virtual('courses', {
  ref: 'Course',
  localField: '_id',
  foreignField: 'student',
  justOne: false
})

const Student = mongoose.model('Student', studentSchema);

const courseSchema = new mongoose.Schema(
  {
    name: {
      type: String,
      required: true,
    },
    student: {
      type: mongoose.Schema.Types.ObjectId,
      ref: 'Student',
      required: true,
    }
  },
  {
    timestamps: true,
  }
);

mongoose.model('Course', coursesSchema)

Student.js

const teacherSchema = new mongoose.Schema(
  {
    name: {
      type: String,
      required: true,
      unique: true,
    },
  },
  {
    timestamps: true,
  }
);

teacherSchema.virtual('students', {
  ref: 'Student',
  localField: '_id',
  foreignField: 'teacher',
  justOne: false
})

const Teacher = mongoose.model('Teacher', teacherSchema);

const studentSchema = new mongoose.Schema(
  {
    name: {
      type: String,
      required: true,
    },
    teacher: {
      type: mongoose.Schema.Types.ObjectId,
      ref: 'Teacher',
      required: true,
    },
  },
  {
    timestamps: true,
  }
);

menuItemSchema.virtual('courses', {
  ref: 'Course',
  localField: '_id',
  foreignField: 'student',
  justOne: false
})

const Student = mongoose.model('Student', studentSchema);

const courseSchema = new mongoose.Schema(
  {
    name: {
      type: String,
      required: true,
    },
    student: {
      type: mongoose.Schema.Types.ObjectId,
      ref: 'Student',
      required: true,
    }
  },
  {
    timestamps: true,
  }
);

mongoose.model('Course', coursesSchema)

Course.js

const teacherSchema = new mongoose.Schema(
  {
    name: {
      type: String,
      required: true,
      unique: true,
    },
  },
  {
    timestamps: true,
  }
);

teacherSchema.virtual('students', {
  ref: 'Student',
  localField: '_id',
  foreignField: 'teacher',
  justOne: false
})

const Teacher = mongoose.model('Teacher', teacherSchema);

const studentSchema = new mongoose.Schema(
  {
    name: {
      type: String,
      required: true,
    },
    teacher: {
      type: mongoose.Schema.Types.ObjectId,
      ref: 'Teacher',
      required: true,
    },
  },
  {
    timestamps: true,
  }
);

menuItemSchema.virtual('courses', {
  ref: 'Course',
  localField: '_id',
  foreignField: 'student',
  justOne: false
})

const Student = mongoose.model('Student', studentSchema);

const courseSchema = new mongoose.Schema(
  {
    name: {
      type: String,
      required: true,
    },
    student: {
      type: mongoose.Schema.Types.ObjectId,
      ref: 'Student',
      required: true,
    }
  },
  {
    timestamps: true,
  }
);

mongoose.model('Course', coursesSchema)

在我的路由器中，我想创建一个如下所示的对象，并将其返回给用户：

{
    <teacherName>: [
        <studentName1>: [<courseName1>, <courseName2>, <courseName3>],
        <studentName2>: [<courseName1>, <courseName2>, <courseName3>]
    ]
}

---

但是，由于还有另一个表，有没有办法填充学生的课程，以便我可以访问所有3个：老师、她的学生和他们的每门课程。

您可以使用

.populate（）

进行深入了解，如下所示：

Teacher.findOne({_id: req.params.teacherId})
  .populate({ 
     path: 'students',
     populate: {
       path: 'courses'
     } 
  })
  .exec(function(err, docs) {});

进一步文件：