Meteor mongodb $inc with update

问题

I have this mongo collection and vars:

items:{
 type_one: 0,
 type_two: 0
}

var valueOne = 1;
var nameItem = type_one;

---

I try to update a value, but not work. I tried this:

Collection.update({createdBy: user_id}, {$inc: { items.$.nameItem: valueOne}} );
Collection.update({createdBy: user_id}, {$inc: { "items.$.nameItem": valueOne}} );
Collection.update({createdBy: user_id}, {$inc: { "items."+nameItem: valueOne}} );
Collection.update({createdBy: user_id}, {$inc: { "items."+nameItem: 1}} );

var object = { $inc: { "items."+nameItem: valueOne} };
Collection.update({createdBy: user_id}, object );
var object = { $inc: { items.$.nameItem: valueOne} };
Collection.update({createdBy: user_id}, object );

But none works and I get this message:

"errorClass {error: 409, reason: "MinimongoError: Cannot apply $inc modifier to non-number", details: undefined, message: "MinimongoError: Cannot apply $inc modifier to non-number [409]", errorType: "Meteor.Error"}"

It's a issue o incompatibility?

回答1:

You need to build your query dynamically using the bracket [] operator. Also "nameItem" must be a string.

var valueOne = 1;
var nameItem = 'type_one';
var inc = {};
inc[ 'items.' + nameItem ] = valueOne;
Collection.update({ createdBy: user_id }, { '$inc': inc } )

回答2:

The only possible reasons I can come up with this that either you inserted number into collection in the form of String or you're trying to increment with String value. Try using parseInt(stringValue) in your code.

来源：https://stackoverflow.com/questions/33968094/meteor-mongodb-inc-with-update