Mongoose model model with a reference array: CastError: discarded in ObjectId with an error for the value "[object Object]"

Question

I am creating a blog site with express.js and mongoosejs. An article may contain one or more categories. When I create a new article, I get an error message:

{ [CastError: Cast to ObjectId failed for value "[object Object]" at path "categories"] message: 'Cast to ObjectId failed for value "[object Object]" at path "categories"', name: 'CastError', type: 'ObjectId', value: [ [object Object] ], path: 'categories' } 

Can anyone help me out? The following code shows below:

The Article model is defined as follows:

 var mongoose = require('mongoose'), Schema = mongoose.Schema; var ArticleSchema = new Schema({ created: { type: Date, default: Date.now}, title: String, content: String, summary: String, categories: [{ type: Schema.ObjectId, ref: 'Category' }] }); mongoose.model('Article', ArticleSchema); 

And the Category model is defined as follows:

 var mongoose = require('mongoose'), Schema = mongoose.Schema; var CategorySchema = new Schema({ parent: { type: Schema.ObjectId, }, name: String, subs: [CategorySchema] }); mongoose.model('Category', CategorySchema); 

When I create a new article and save it like this:

 exports.create = function(req, res) { console.log(req.body); var article = new Article(req.body); article.user = req.user; console.log(article); article.save(function(err) { if (err) { console.log(err); return res.jsonp(500, { error: 'Cannot save the article' }); } res.jsonp(article); }); }; 

When the create function is called, the output of console.log () shows below:

 // console.log(req.body); { title: 'This is title', content: '<p>content here</p>', categories: [ { _id: '53c934bbf299ab241a6e0524', name: '1111', parent: '53c934b5f299ab241a6e0523', __v: 0, subs: [], sort: 1 } ], updated: [ 1405697477413 ] } // console.log(article); { title: 'This is title', content: '<p>content here</p>', _id: 53c93dc5b1c3b8e80cb4936b, categories: [], created: Fri Jul 18 2014 23:31:17 GMT+0800 (中国标准时间) } // console.log(err); { [CastError: Cast to ObjectId failed for value "[object Object]" at path "categories"] message: 'Cast to ObjectId failed for value "[object Object]" at path "categories"', name: 'CastError', type: 'ObjectId', value: [ [object Object] ], path: 'categories' } 

I have a lot of googled, but no luck. Please help me!

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Update: Thanks for Hergo's answer. But if I update an existing article using almoset of the same code, it works fine! What for? Codes are shown below:

 var mongoose = require('mongoose'), Category = mongoose.model('Category'), _ = require('lodash'); exports.update = function(req, res) { console.log(req.body); var article = req.article; article = _.extend(article, req.body); console.log(article); article.save(function(err) { if (err) { return res.jsonp(500, { error: 'Cannot update the article' }); } res.jsonp(article); }); }; 

The output is as follows:

 // console.log(req.body); { _id: '53ca42f418bfb23c1e04df02', summary: 'tttt', title: 'tt', content: '<p>tttt</p>', __v: 2, categories: [ { _id: '53c934bbf299ab241a6e0524', name: '1111' } ], created: '2014-07-19T10:05:40.183Z' } // console.log(article); { _id: 53ca42f418bfb23c1e04df02, title: 'tt', content: '<p>tttt</p>', __v: 2, categories: [ { _id: 53c934bbf299ab241a6e0524, name: '1111', subs: [], sort: 0 } ], created: Sat Jul 19 2014 18:05:40 GMT+0800 (中国标准时间) } 

This is working fine.

Answer 1

Your article outline expects an ObjectIds array:

 var ArticleSchema = new Schema({ ... categories: [{ type: Schema.ObjectId, ref: 'Category' }] }); 

However, req.body does contain a category object:

 categories: [ { _id: '53c934bbf299ab241a6e0524', name: '1111', parent: '53c934b5f299ab241a6e0523', __v: 0, subs: [], sort: 1 } ] 

And Mongoose cannot convert a category object to an ObjectId. That is why you get an error. Make sure the categories in req.body contain only identifiers:

 { title: 'This is title', content: '<p>content here</p>', categories: [ '53c934bbf299ab241a6e0524' ], updated: [ 1405697477413 ] } 

Answer 2

Please use mongoose.Schema.Types.Mixed as the data type of the categories. I had the same problem with saving a data array. he works for me.

 var mongoose = require('mongoose'), Schema = mongoose.Schema; var ArticleSchema = new Schema({ created: { type: Date, default: Date.now}, title: String, content: String, summary: String, categories: [{type: Schema.Types.Mixed }] }); mongoose.model('Article', ArticleSchema);