$push not creating new array field. Using Mongoose

Question

Working on a blog site. In MongoDB my blog posts don't have a comments field to start out. I would like to use $push to add a comments field and add the comment value. The code below doesnt throw any errors, the console.log fires but when I check the fields in MongoDB nothing has changed.

Post.findByIdAndUpdate(
    postid,
    {$push:{"comments": comment}},
    {new: true},
    function(err, added){
        if(err){
            throw err;
        } else {
            console.log('\n-------- Comment Added ----------\n');
            res.redirect('/');
        }
    }
);

EDIT: I figured out that this is because I didn't have a comment field set up in the schema. But now that I added it, how do I deal with the comment field being undefined initially? I have jade code that lists all of the comments if they exist:

if post.comments
        h3 Comments
        each comment, i in comments
            .comment
                p.comment-name #{comment.name}
                p.comment-text #{comment.body}

But I get error:

p.comment-text #{comment.body} Cannot read property 'length' of undefined

Leo Fabrikant · Accepted Answer · 2015-12-29 07:10:39Z

1

Thanks Mariya! The problem is that you cant push new fields into mongoose models. All fields have to be defined before hand.

answered Dec 29, 2015 at 7:10

Leo Fabrikant

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Comments

Mariya James · Accepted Answer · 2015-12-29 05:12:08Z

0

Try with $addToSet instead of $push.

Post.findByIdAndUpdate(
postid,
{$addToSet:{"comments": comment}},
{new: true},
function(err, added){
    if(err){
        throw err;
    } else {
        console.log('\n-------- Comment Added ----------\n');
        res.redirect('/');
    }
});

answered Dec 29, 2015 at 5:12

Mariya James

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5 Comments

Leo Fabrikant Over a year ago

but theres no array there in the first place

Leo Fabrikant Over a year ago

doesnt addtoset just add to an existing array instead of creating a new field?

Leo Fabrikant Over a year ago

Thats what i JUST figured out! There was no comment field in the schema :) I just added it but now I have another problem on the Jade page. The Jade page is supposed to show comments for a post IF there are comments. But when there are no comments, it has trouble dealing with it because it is undefined. Can I set it to something other than undefined in the schema?

Mariya James Over a year ago

You defined comment field as array right? So you can check by its length whether it has elements or not

Leo Fabrikant Over a year ago

OK got it working by checking length now. The Jade error was a separate issue. The loop should be each comment, i in post.comments

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