CODEWITHSUNDEEP
iosswiftparse-platform
Bernard
Bernard

Reputation: 4580

How to decrement a value in Parse cloud using iOS Swift?

Maybe this question is very basic but I am looking for a nice way to decrement a value. I have a column called "credit" in _User table. Default value is 0. I want to decrement one credit from this column. This is what I have so far:

            //Decrement user credit
            let query2 = PFQuery(className:"_User")
            query2.whereKey("user", equalTo: PFUser.currentUser()!)
            query2.getFirstObjectInBackgroundWithBlock {
                (object: PFObject?, error: NSError?) -> Void in
                if error != nil
                {
                    PFUser.currentUser()!["credit"] = (PFUser.currentUser()!["credit"] as! Int) - 1
                    self.navigationController?.popViewControllerAnimated(true)
                }
            }

Upvotes: 1

Views: 611

Answers (2)

PAD
PAD

Reputation: 2330

object.decrementKey("key", byAmount: myIntValue)
has been removed from Parse SDK methods (at least with iOS). The doc isn't up-to-date anymore.

You can now decrement by incrementing with a negative value, like this : 

object.incrementKey("key", byAmount: NSNumber(value: -1 * myIntValue))

Upvotes: 1

kRiZ
kRiZ

Reputation: 2316

To decrement, and also increment, a particular field, Parse has some built-in methods:

  • object.incrementKey("key")
  • object.incrementKey("key", byAmount: 2) // any int amount
  • object.decrementKey("key")
  • object.decrementKey("key", byAmount: 2) // any int amount

So after fetching your user object in that query, your code will become:

PFUser.currentUser().incrementKey("credit")
PFUser.currentUser().saveInBackgroundWithBlock {
  (success: Bool, error: NSError?) -> Void in
  if (success) {
    // The credit key has been incremented
  } else {
    // There was a problem, check error.description
  }
}

See Parse documentation here on Counters.

Upvotes: 1

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