Struggling to fill in fields using express and Mongodb

Question

Struggling to fill in fields using express and Mongodb

I am facing an issue with populating the fields of two models, Post and User.

const PostSchema = new Schema({
    text: { 
        type: String 
    },
    author: {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'user'
    }
})

const UserSchema = new Schema({
    username: {
        type: String, 
    }
})

router.post('/', async (req,res) => {
    try {
        let joe = new User({username: "joe"})
        await joe.save()
        
        let postText = {text: "my name is joe", author: joe._id}
        let postByJoe = new Post(postText)
        await postByJoe.save()

        let users = User.find().populate('author') 
        res.json({users})
    } catch (error) {
        console.error(error.message)
        res.json(error.message)
    }
    
})

I've encountered a strange error that I can't figure out. It seems to be related to JSON conversion. Any assistance would be highly appreciated.

"Converting circular structure to JSON\n --> starting at object with constructor 'NativeTopology'\n | property 's' -> object with constructor 'Object'\n | property 'sessionPool' -> object with constructor 'ServerSessionPool'\n --- property 'topology' closes the circle"

javascript mongodb express mongoose

Answer 1

Answer №1

Your schema contains something unique - you can only populate the Schema.Types.ObjectId field within it. It appears that you are attempting to populate the author field of the Post model.

To correct this, replace this line

let users = User.find().populate('author')

with

let users = Post.find().populate('user')

. Your code should resemble the following:

router.post('/', async (req,res) => {
try {
    let joe = new User({username: "joe"})
    await joe.save()
    
    let postText = {text: "my name is joe", author: joe._id}
    let postByJoe = new Post(postText)
    await postByJoe.save()

   let data = await Post.find().populate('user') 
    // map through the object returned
    const users = data.map((user) => user)
    res.json({users})
} catch (error) {
    console.log(error.message)
    res.json(error.message)
}

})

For more information on mongoose population, visit this link.

Answer 2

Your schema contains something unique - you can only populate the Schema.Types.ObjectId field within it. It appears that you are attempting to populate the author field of the Post model.

To correct this, replace this line

let users = User.find().populate('author')

with

let users = Post.find().populate('user')

. Your code should resemble the following:

router.post('/', async (req,res) => {
try {
    let joe = new User({username: "joe"})
    await joe.save()
    
    let postText = {text: "my name is joe", author: joe._id}
    let postByJoe = new Post(postText)
    await postByJoe.save()

   let data = await Post.find().populate('user') 
    // map through the object returned
    const users = data.map((user) => user)
    res.json({users})
} catch (error) {
    console.log(error.message)
    res.json(error.message)
}

})

For more information on mongoose population, visit this link.

Struggling to fill in fields using express and Mongodb

Answer №1

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