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Rajesh Royal
Rajesh Royal

Posted on • Edited on

Update an object in nested array in MongoDB

#mongodb #database #javascript #node

Hello Reader 👋

To update an object inside a nested array in MongoDB you can use this approach, Its well tested and working.

Case:

Update nested array objects. See below picture for a better Idea what we are going to do. We will update the object which is nested by 3 levels of array.

{ discussionList[ discussionList [ { object-value-to-be-updated. } ] ] }
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mongodb - update an object inside multilevel nested array

Solution: 

public courseCategoryPostCommentReplyUpdate(operation: CommentReplyUpdateMutation): Promise<IDocumentUpdateType> { return this.courseCategoryPostCommentsModel.updateOne( { "postId" : operation.postId, 'discussionList': { '$elemMatch': { '_id': operation.commentId, "discussionList._id": operation.replyId } } }, { $set: { "discussionList.$[outer].discussionList.$[inner].payload": operation.payload, "discussionList.$[outer].discussionList.$[inner].isUpdated": true, "discussionList.$[outer].discussionList.$[inner].commentUpdateTime": new Date() } }, { arrayFilters: [ { "outer._id": operation.commentId}, {"inner._id": operation.replyId} ] } ); }
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FootNotes - this code is to update the reply of a comment.

That's how you can perform operations on an object in nested array in mongoDB document. You can also update/delete the objects which are having the more level of nesting by just modifying the query.

Example of delete and get

Delete 
// Informational Note: // Delete nested array values in mongodb public courseCategoryPostCommentReplyDelete(operation: CommentReplyDeleteMutation): Promise<IDocumentUpdateType> { return this.courseCategoryPostCommentsModel.updateOne( { 'postId': operation.postId, 'discussionList': { '$elemMatch': { '_id': operation.commentId, 'discussionList._id': operation.replyId } } }, { $pull: { 'discussionList.$[outer].discussionList': { user: operation.userId, _id: operation.replyId } } }, { arrayFilters: [ { 'outer._id': operation.commentId } ], multi: false } ); } }
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GET 

public courseCategoryPostCommentRead(postId: string): Promise<IComment> { return this.courseCategoryPostCommentsModel.findOne<IComment>({ postId: postId }).populate('discussionList.user').populate('discussionList.discussionList.user').exec(); }
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I was using GraphQL. You may need to iterate over the result and show the comments/replies as per that.

Please let me know if the code needs an explanation. Thanks 🙂

Top comments (6)

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linkitsoftoffice profile image
linkitsoftoffice •

how can I use pull in this? I tried modifying the query but it prompts me up with errors like, pull to a non array value further modifying it gives me, Could not find path "undefined.0.userId" in schema.

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rajeshroyal profile image
Rajesh Royal •

@linkitsoftoffice I have updated the post.

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saheb24027824 profile image
Uifoxes •

Data :

[ { _id: ObjectId("641050763af868f204dd3ce6"), username: 'erkin', email: 'erkin-07@hotmail.com', password: 'b', playlists: [ { _id: 58, name: 'asdsa', date: '09-01-15', musics: [ { name: 'INNA - Cola Song (feat. J Balvin)', duration: '3.00' }, { name: 'blabla', duration: '3.00' }, { name: 'new', duration: '3.00' } ] } ] } ]
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Query

db.test.updateOne( { username: 'erkin', playlists:{$elemMatch: {name:"asdsa" , "musics.name":"blabla"}} }, { $set:{"playlists.$[outer].musics.$[inner].duration":"4.00"} }, { $arrayFilters:[{"outer.name":"asdsa"},{"inner.name":"blabla"}] } )
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Output
MongoServerError: No array filter found for identifier 'outer' in path 'playlists.$[outer].musics.$[inner].duration'

Please help to correct the error

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ssembara profile image
Sebastianus Sembara •

where do we get the inner and outer variables?

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rajeshroyal profile image
Rajesh Royal • • Edited

You don't have to get those variables.

The inner and outer variables are used as placeholders. If you see in the arrayFilter we are modifying the ._id part of these variables.

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saheb24027824 profile image
Uifoxes •

found the issue $arrayFilters , it should be arrayFilters