獲取指向給定對象的所有Parse.Relations

Question

我正在使用Parse.Relation在主題下對用戶進行分組。如何檢索指向給定用戶的所有主題（topic.relation）？

問題是關於在單個調用/回調中執行此操作。

// 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. 

Answer 1

構造對Topic類的查詢，並添加equalTo約束。

var query = new Parse.Query(Topic); 
query.equalTo("friend", user); 
query.find({success: function (returnedTopics) { 
    ... 
    }, 
    error: function (...) { 
    } 
}); 

這將返回包含其朋友關係中的用戶的所有Topic對象。