Question

我试图通过查询用户和项目的两个对象来防止重复项目被复制。如果它们存在则不重复但如果它不存在则创建它的实例。我知道它会继续运行，并根据解析中的项目数量生成多个重复项。有谁知道如何防止它重复这些值？

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

您可以将NSSet用于存储唯一对象。

Answer 2

我并不是要回答我自己的问题，但我明白了。它现在正按计划运作。这是我的代码。它现在可以正常工作，但是我再次尝试我的早期解决方案，但事后并没有。这看起来对每个人都有好处吗？这会让我后来头痛吗？

 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")
        }

    }

}

如何查询解析特定项目并防止重复保存

2 个答案: