Trying to split array of objects based on a common key of the objects with swift

Question

I'm completely lost with swift. I am trying to split an array of objects (retrieved using the Parse SDK) based on a common key. Basically I would like to make a COUNT + GROUP BY, but I could not find a way to make a GROUP BY with the Parse SDK, so I am trying to group the objects and count them by the code. But first, what I am writing looks horrible, and secondly that does not even compile and I can't understand why.

This is the code I'm using

var groupedEntries = [String: [String: AnyObject?]]()

...

let query = PFQuery(className: "Entry")
query.findObjectsInBackgroundWithBlock { (objects: [AnyObject]!, error: NSError!) -> Void in
   if error == nil {

      var groupingKey: String
      for object in objects {

         groupingKey = object[groupingKey] as String
         if self.groupedEntries[groupingKey] != nil {
            self.groupedEntries[groupingKey]["count"] = self.groupedEntries[groupingKey]["count"] + 1
         } else {
            self.groupedEntries[groupingKey]["count"] = 1
         }
      }
      self.tableView.reloadData()
   }
}

And the compiler gives the following error : 'String' is not convertible to 'DictionaryIndex'. Whatever I try I get an error related to optionals or wrapping.

Thanks to anybody that will help me :)

codester · Accepted Answer · 2014-10-04 14:57:42Z

1

While using subscript the Dictionary returns optional of given value type so you need to unwrap it.You need to take the extra variable i used somevar.See below code

var groupedEntries = [String: [String: AnyObject?]]()

@IBAction func changeImage(sender: AnyObject){
    var objects:[AnyObject]!
    var groupingKey: String //= "abc" Intialize before using
    //var countryCode: String   //= "abc" not defined in your code

    for object in objects {

        groupingKey = object[groupingKey] as String
        if self.groupedEntries[groupingKey] != nil {
            var somevar = self.groupedEntries[groupingKey]!
            somevar["count"] = (somevar["count"]! as Int) + 1
        } else {
            self.groupedEntries[groupingKey] = ["count":1]
        }
    }
}

I do not know about your logic but this code compiles well.

edited Oct 4, 2014 at 14:57

answered Oct 4, 2014 at 12:54

codester

37.2k11 gold badges77 silver badges72 bronze badges

Sign up to request clarification or add additional context in comments.

7 Comments

LiohAu Over a year ago

Well, this compile, but generates an EXC_BAD_INSTRUCTION exception on the "else" statement (fatal error: unexpectedly found nil while unwrapping an Optional value).

codester Over a year ago

you should check self.groupedEntries[countryCode] for nil also if nil need to intialize it

codester Over a year ago

It is improvement but these kind of stuff really get mess if you do not use good techniques.Study good Json parsing library code

codester Over a year ago

Sorry used countryCode instead of groupingKey.Not saw your edit. edited answer

vacawama Over a year ago

@codester, in the else clause, self.groupedEntries[groupingKey] is nil as established by the if. I suggest first setting it to a new dictionary.

|

Collectives™ on Stack Overflow

Trying to split array of objects based on a common key of the objects with swift

1 Answer 1

7 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

7 Comments

Your Answer

Sign up or log in

Post as a guest

Related