mongodb - Setting a value post update with the `findOneAndUpdate` Mongoose hook -

i trying use findoneandupdate hook mongoose (discussed in detail here), although i'm having problems trying set value post update.

for example:

myschema.findoneandupdate({_id: fj394hri3hfj}, {$push: {comments: mynewcomment}}) 

will trigger following hook:

myschema.post('findoneandupdate', function(result) {     this.update({}, { totalnumberofcomments: result.comments.length }); }); 

although, hook $push comments mynewcomment again, therefore making duplicate entry.

i use this.update({}, {....}) instead of this.findoneandupdate({}, {....}) within hook post hook not called infinitely.

the totalnumberofcomments set length of comments.length.

so seems if this.update({}, {....}) pushing more update fields existing update fields on this.

how can set totalnumberofcomments within hook instead of re-pushing comments again?

the issue seems in update query wrote in post findoneandupdate hook. try replacing with,

myschema.post('findoneandupdate', function(result) {     this.totalnumberofcomments = this.result.comments.length;     this.save(function(err) {        if(!err) {           console.log("document updated");        }     }); }); 

and should work.

i suggest, using find , save updating document instead of findoneandupdate , post hook.

---

edit:

in case need use find , save, can replace above code with:

myschema.findbyid(fj394hri3hfj, function(err, doc){      doc.comments.push(mynewcomment);     doc.totalnumberofcomments += 1;     doc.save(function(err){         console.log("document updated");            });  }); 

and should work.