Swift Firebase Completion Block Infinite Loop

Question

I am making an app that holds many books in firebase. I am getting a very strange problem wherein my application will infinite loop when adding a new book and keep adding the same book as fast as it can. If there would be any way that a more experienced person could take a look, I would be very grateful.

@IBAction func userHasBook(sender: AnyObject) { // Called after filling a new book form

    let email = FIRAuth.auth()?.currentUser?.email!
    let school = email!.substringWithRange(Range(email!.characters.indexOf("@")!.advancedBy(1) ..< email!.characters.indexOf(".")!)) // for db organization


    //A few lines here that ensure that the fields are filled correctly (clutter so i didn't add them)


    ref.child(school).observeEventType(.Value, withBlock: { (snapshot) in
        self.bookIndex = snapshot.value!["numSelling"] as! Int
        self.addSellingBook(); // we now know it is done finding the value, right?
    }) { (error) in
        print(error.localizedDescription)
    }
}

func addSellingBook(){
    let bookRef = self.ref.child(school).child("selling").child(Int(self.bookIndex).description)

    let book : [NSObject : AnyObject] = ["uid": (FIRAuth.auth()?.currentUser?.uid)!,
                "title": self.titleField.text!,
                "authors": self.authorsField.text!,
                "edition": self.editionField.text!,
                "price": self.priceField.text!,
                "isbn" : self.isbn] // this is the data that is added infinitely many times

    bookRef.updateChildValues(book, withCompletionBlock: { (NSError, FIRDatabaseReference) in //update the book in the db
        let newIndex = self.bookIndex + 1
        self.ref.child(self.school).child("numSelling").setValue(newIndex, withCompletionBlock: { (NSError, FIRDatabaseReference) in // after that update the index
            self.performSegueWithIdentifier("backToMain", sender: nil) // and after that go back to main 
        })
    })

Thanks a ton and ask me if you need anything more!

EDIT: JSON BEFORE BELOW

   {
        "colorado" : {
            "numBuying" : 0,
            "numSelling" : 0,
        "users" : {
                "2nU0jp4ITjgQ6ElSQWc7t5qj62t1" : {
                    "email" : "vhegde@colorado.edu"
                }
            }
        },
        "creek" : {
            "numBuying" : 0,
            "numSelling" : 2,
            "selling" : [ {
            "authors" : "A. S. A. Harrison",
            "edition" : "Only Edition",
            "isbn" : "1101608064",
            "price" : "5.00",
            "title" : "The Silent Wife",
            "uid" : "eJvdVx3J8EYZPH3mlbYLBcPDkD12"
            }, {
            "authors" : "Jamie McGuire",
            "edition" : "Only Edition",
            "isbn" : "1476712050",
            "price" : "5.00",
            "title" : "Beautiful Disaster",
            "uid" : "eJvdVx3J8EYZPH3mlbYLBcPDkD12"
            } ],
        "users" : {
                "eJvdVx3J8EYZPH3mlbYLBcPDkD12" : {
                    "email" : "vhegde@creek.edu"
                }
            }
        }
    }

Then, I add another book (index of 2) and rather it keeps adding infinite books and infinitely increments index (numSelling). I don't want to post that JSON as it is like 300 lines long.

Answer 1

弄清楚了，而不是使用observeEventType，必须使用observeSingleEventOfType

Answer 2

Please change Your code as i have implemented in below method to set online/offline.

// MARK: - User Online/Offline

func setUserOnlineOffline(userId: String!, isOnline: Bool!) {
        Let ref = FIRDatabase.database().reference().child(FIRPATH_USER_USERID_DETAILS(userId))

        if isOnline == true {
            ref.updateChildValues(["last_seen": "Online"])
        } else {
            ref.updateChildValues(["last_seen": FIRServerValue.timestamp()])
        }

        ref.onDisconnectUpdateChildValues(["last_seen": FIRServerValue.timestamp()])
    }

//note: here you have to set string, so please replace dictionary of nsobject with string .. might be helpful to you