SomeSchema.statics.findAndModify = function (query, sort, doc, options, callback) {
    return this.collection.findAndModify(query, sort, doc, options, callback);
};

mongoose.model('Some',SomeSchema);

然后findAndModify

Some.findAndModify({}, [], { $inc: { amount: 1 } }, {'new':true}, function (err) {
    if (err) throw err;
});

似乎成功的给amount加了1,但是我想直接取得新amount的值,有办法么?