获取指向给定对象的所有解析。
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12-12-2019 - |
题
我在主题下使用Parse.Relation
到组用户。如何检索具有指向给定用户的生成的所有主题?
问题是在单个呼叫/回调中执行此操作。
// first add() a User object to the Topic's Parse.Relation
this.friendRelation = this.topic.relation("friend");
this.friendRelation.add(user);
// save the Topic to save its newly added .relation to Parse/Mongo
this.topic.save();
// iterate by adding the same User to several Topics
// (...)
// then you want to retrieve all Parse.Relations of all Topics where that
// specific user is pointed to
// the non-optimized way is to traverse every row in the Topics index
// and query each topic for its relations to find matching pointers to our user,
// which means that the number of calls is bound to the number of rows – fine for
// 10 topics in Mongo but passed 100 it won't be tolerable.
. 解决方案
构造主题类的查询,并添加一个等于约束。
var query = new Parse.Query(Topic);
query.equalTo("friend", user);
query.find({success: function (returnedTopics) {
...
},
error: function (...) {
}
});
.
这将返回在其朋友关系中包含用户的所有主题对象。
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