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ViewsError while deleting a value of element in mongoDB array using filter function?
I tried to find the solutions over here but unable to get success while using $pull as the array values I have does not contain `mongo_id'.
So the scenario is that , I am trying to delete the specific comment of the particular user which I am passing through query params. M
My mongo data looks like this:
Now I am making API Delete request like this : http://localhost:8000/api/articles/learn-react/delete-comment?q=1 on my localhost .
ANd finally my code looks like this:
import express from "express";
import bodyParser from "body-parser";
import { MongoClient } from "MongoDB";
const withDB = async (operations, res) => {
try {
const client = await MongoClient.connect(
"mongodb://localhost:27017",
{ useNewUrlParser: true },
{ useUnifiedTopology: true }
);
const db = client.db("my-blog");
await operations(db);
client.close();
} catch (error) {
res.status(500).json({ message: "Error connecting to db", error });
}
};
app.delete("/api/articles/:name/delete-comment", (req, res) => {
const articleName = req.params.name;
const commentIndex = req.query.q;
withDB(async(db) => {
try{
const articleInfo = await db.collection('articles').findOne({name:articleName});
let articleAllComment = articleInfo.comments;
console.log("before =",articleAllComment)
const commentToBeDeleted = articleInfo.comments[commentIndex];
//console.log(commentToBeDeleted)
// articleAllComment.update({
// $pull: { 'comments':{username: commentToBeDeleted.username }}
// });
articleAllComment = articleAllComment.filter( (item) => item != commentToBeDeleted );
await articleAllComment.save();
console.log("after - ",articleAllComment);
//yaha per index chahiye per kaise milega pta nhi?
//articleInfo.comments = gives artcle comment
res.status(200).send(articleAllComment);
}
catch(err)
{
res.status(500).send("Error occurred")
}
},res);
});
I have used the filter function but it is not showing any error in terminal but also getting 500 status at postman.
Unable to figure out the error?
1 answers
Answer question0
I believe you'll find a good answer here: https://stackoverflow.com/a/4588909/9951599
Something to consider...
You can use MongoDB's built-in projection methods to simplify your code. https://docs.mongodb.com/manual/reference/operator/projection/positional/#mongodb-projection-proj.-
By assigning a "unique ID" to each of your comments, you can find/modify the comment quickly using an update command instead of pulling out the comment by order in the array. This is more efficient, and much simpler. Plus, multiple read/writes at once won't interfere with this logic during busy times, ensuring that you're always deleting the right comment.
Solution #1: The recommended way, with atomic operators
Here is how you can let MongoDB pull it for you if you give each of your comments an ID.
await db.collection('articles').updateOne({ name:articleName },
{
$pull:{ "comments.id":commentID }
});
// Or
await db.collection('articles').updateOne({ name:articleName, "comments.id":commentID },
{
$unset:{ "comments.$":0 }
});
Solution #2 - Not recommended
Alternatively, you could remove it by index:
// I'm using "3" here staticly, put the index of your comment there instead.
db.collection('articles').updateOne({ name:articleName }, {
$unset : { "comments.3":0 }
})
I do not know why your filter is erroring, but I would recommend bypassing the filter altogether and try to utilize MongoDB's atomic system for you.