在MongoDB中更新(递增)子文档中的值

本文介绍了在MongoDB中更新(递增)子文档中的值的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

如果我有一个包含文档和子文档的MongoDB集合，如图所示:

If I have a MongoDB collection with documents and sub-documents, as illustrated:

而且，如果我想在每次调用该方法时将损坏"增加1，则:

And, if I want to increment the "damage" by 1 each time the method is called:

private final static void incrementCount(String docID, String subDocID) { BasicDBObject query = new BasicDBObject(); query.put("_id", docID); query.put("items.id", subDocID); BasicDBObject incValue = new BasicDBObject("damage", 1); // or "items.damage" ??? BasicDBObject intModifier = new BasicDBObject("$inc", incValue); badgesCollection.update(query, intModifier, false, false, WriteConcern.SAFE); }

问题:我是指损坏"还是"items.damage"?

Question: do I refer to "damage" or "items.damage" ?

推荐答案

都没有.如果只想增加具有匹配的subDocID的items数组元素的damage值，则需要使用$ 位置运算符，以将该元素标识为$inc运算符.就是这样:

Neither. If you want to increment just the damage value for the items array element with the matching subDocID you need to use the $ positional operator to identify that element to the $inc operator. So it's:

"items.$.damage"