如何查詢特定項目的解析並防止重複被保存

Question

我試圖通過查詢兩個對象用戶和項目來防止重複的項目被複制。如果它們存在，則不要複製，但如果它不存在，則創建它的一個實例。我知道它會一直運行，並根據解析中出現的項目數量做出多個重複項。有誰知道如何防止它重複這些值？

func addUserToItem(userID:String,myItemID:String,currCommit:Float) {  
    let query = PFQuery(className: "UserToItem") 
    query.findObjectsInBackgroundWithBlock({ (objects, error) -> Void in 

     if error != nil { 
      print("Got an error here") 
     } else {      
      print(objects) 

      for object in objects! { 
       print("ok") 
       guard let userInformation = object.objectForKey("username") as? String else { 
        print("didnt work") 
        return 
       } 

       guard let itemInformation = object.objectForKey("currentItem") as? String else { 
        print("didnt work2") 
        return 
       } 
       var isThere = false 

       if (userInformation == userID) && (itemInformation == myItemID) {      
        print("It exists") 
        isThere = true          
       } 

       if !isThere { 
        print("it worked") 

        let myProduct = PFObject(className: "UserToItem") 
        myProduct.setObject(userID, forKey: "username") 
        myProduct.setObject(myItemID, forKey: "currentItem") 
        myProduct.setObject(currCommit, forKey: "UserCommit") 
        myProduct.setObject(true, forKey: "Viewed")     
        myProduct.saveInBackground() 
        isThere = true 
       }      
      }   
     } 
    }) 
} 

Answer 1

我不是故意回答我自己的問題，但我明白了。它按計劃正在工作。這是我的代碼。它現在可以工作，但是我再次嘗試了我的早期解決方案，除非事後沒有解決。這對所有人都好嗎？這會讓我頭疼嗎？

func addUserToItem(userID:String,myItemID:String,currCommit:Float) { 



    let query = PFQuery(className: "UserToItem") 


    query.whereKey("username", equalTo: userID) 
    query.whereKey("currentItem", equalTo: myItemID) 
    query.getFirstObjectInBackgroundWithBlock { (object, error) -> Void in 



     if error != nil { 
      let myProduct = PFObject(className: "UserToItem") 

      myProduct.setObject(userID, forKey: "username") 
      myProduct.setObject(myItemID, forKey: "currentItem") 
      myProduct.setObject(currCommit, forKey: "UserCommit") 
      myProduct.setObject(true, forKey: "Viewed") 

      myProduct.saveInBackground() 
     } else { 
      print("it exists") 
     } 

    } 

} 

Answer 2

您可以使用NSSet存儲唯一對象。