node js mongo search

Question

我想在主题模型中搜索一个id，该模型有一个教师ID数组如下

var Classroom = require('./classroom');
var Teacher = require('./teacher');
var ClassSectionSchema = new Schema({
 title : String,
 teacher_id : [{type: Schema.Types.ObjectId, ref: 'Teacher'}]

});

我想在删除之前搜索每位老师，但如果老师在班级部分连接我不想删除它，我尝试了以下

router.post('/delete',function(req,res){
var teacher_id= req.body.selected;

Class_section.findOne({teacher_id:teacher_id},function(err,subject){
    if(err){
        console.log(err);
        res.json({status:"error", message :"error occurred"});
        return;
    }else if(subject){
        res.json({status:"error", message:"teacher has class"});
        return;
    }else{
        Teacher.remove({_id:teacher_id},function(err){
            if(err){
                console.log(err);
                res.json({status:"error", message :"error occurred"});
                return;
            }else{
                res.json({status:"success",message: "teacher deleted"});
                return;
            }
        })
    }
})
})

以前的代码仅在课程部分有一个教师ID时有效，但如果教师ID中有两个教师，教师会被删除

Answer 1

var mongoose = require('mongoose'); 
var ObjectId = mongoose.Types.ObjectId();

router.post('/delete',function(req,res){
  var queryObj = {};
  if(req.body.selected){
     queryObj.teacher_id = {
        $in:[new ObjectId(req.body.selected)]
     }
}

Class_section.find(queryObj,function(err,subject){
if(err){
    console.log(err);
    res.json({status:"error", message :"error occurred"});
    return;
}else if(subject.length > 0){
    res.json({status:"error", message:"teacher has class"});
    return;
}else if(subject.length == 0){
    Teacher.remove({_id:teacher_id},function(err){
        if(err){
            console.log(err);
            res.json({status:"error", message :"error occurred"});
            return;
        }else{
            res.json({status:"success",message: "teacher deleted"});
            return;
        }
    })
}
})
})