ObjectId from mongodb will not correct by using flatten methods

[vcxiaohan]

No description provided.

[antony]

Had the same problem, so I fixed it in #61 - let me know if it works for you

[vcxiaohan]

It not work for me!
The mongodb data like this:

{ 
_id: 598124cbfd5a7c47dcae586f,
  updatedAt: 2017-08-02T01:03:07.988Z,
  createdAt: 2017-08-02T01:03:07.988Z,
  title: '111'
} 

When I use var flat = require('flat'); var _obj = flat.flatten(obj), the result like this:

{
 '_id._bsontype': 'ObjectID',
  '_id.id': <Buffer 59 81 24 cb fd 5a 7c 47 dc ae 58 6f>,
  updatedAt: 2017-08-02T01:03:07.988Z,
  createdAt: 2017-08-02T01:03:07.988Z,
  title: '111'
 }

Suggest: You just need to convert type from ObjectId to String by coding like this:

if(key == '_id' && isBuffer(key)) {
obj[key] = (obj[key]).toString()// this will convert type from ObjectId to String
}

And I will try again after you fixed this.

[antony]

Works fine for me, It's already in production on our application :)

You need to:

npm install vendigo-group/flat # use my branch until this PR is merged.

Then use the following code:

const coercion = [{
  test: (key, value) => value && value._bsontype === 'ObjectID',
  transform: value => { return value.valueOf().toString() }
}]

flatten(yourobject, { coercion: coercion })

There are tests covering the code in the pull request, so feel free to inspect those to help you.

The code you have suggested, by the way, has a number of issues:

1. .toString does not unwrap ObjectIDs. valueOf does. .toString() on its own will print out the object.
2. Your code assumes that every _id field is an ObjectID. We can't make sweeping assumptions like this
3. Your code assumes that only _id fields are ObjectIDs. This also isn't true (reference field types are ObjectID, for example)
4. For some reason, you are checking isBuffer on the key, not the value. This will return false. The key is _id which is a String.

[juanjoDiaz]

In #64 I've proposed yet another solution using the toJSON method.
Since flatten is a library to flatten JSON objects, it makes sense to use the toJSON method which is used by browsers/node JSON utility object.

[antony]

@juanjoDiaz your solution is fine - however its scope is very small - there are precious few objects which are generous enough to provide a toJSON method. I'm also not sure it's always the user's preference to use the toJSON method. It's good to provide the user with a choice.

Also - as a side note, you left a console.log in your code

[juanjoDiaz]

damn! good catch...
Some eslint would have been useful here...

Yeah. Certainly the scope is small. The idea was to modify just the minimum and cover the most possible cases. As I mention in the PR, 'm happy with any solution that cover this use case :)

[antony]

I've decided to fork and republish as flatley, as I get the feeling that this project is abandoned.

https://www.npmjs.com/package/flatley
https://www.github.com/antony/flatley

Let me know if you have further issues (ideally provide me with a reproduction) and I'll endeavour to fix them.