What's Mongoose error Cast to ObjectId failed for value XXX at path "_id"?
Full error message
When sending a request to /customers/41224d776a326fb40f000001 and a document with _id 41224d776a326fb40f000001 does not exist, doc is null and I'm returning a 404:
Controller.prototype.show = function(id, res) {
this.model.findById(id, function(err, doc) {
if (err) {
throw err;
}
if (!doc) {
res.send(404);
}
return res.send(doc);
});
};
However, when _id does not match what Mongoose expects as "format" (I suppose) for example with GET /customers/foo a strange error is returned:
CastError: Cast to ObjectId failed for value "foo" at path "_id".
So what's this error?Solutionsource: stackoverflow \u2197
Mongoose's findById method casts the id parameter to the type of the model's _id field so that it can properly query for the matching doc. This is an ObjectId but "foo" is not a valid ObjectId so the cast fails. This doesn't happen with 41224d776a326fb40f000001 because that string is a valid ObjectId. One way to resolve this is to add a check prior to your findById call to see if id is a valid ObjectId or not like so: if (id.match(/^[0-9a-fA-F]{24}$/)) { // Yes, it's a valid ObjectId, proceed with `findById` call. }
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