How to grab ObjectId from object in parse and present it as string in swift

Question

Why am I not able to present the "ObjectId" from an Object from parse as a String in swift even though it is naturally already a string? Here is the logic I a attempting to you use:

//MARK: Fetch ObjectId Strings From Parse
    func fetchObjectIdString() {

        let query = PFQuery(className: "Books")
        query.whereKey("genreName", equalTo: self.genreName)
        query.findObjectsInBackgroundWithBlock { (objects, error) -> Void in

            if error == nil {

                if let objects = objects as [PFObject]! {

                    for oneObj in objects {

                        let ObjectIdFromParse = oneObj["objectId"] as! String
                        let SingleObjectId = SixthBook()
                        SingleObjectId.objectIdString = ObjectIdFromParse
                        self.arrayOfObjectId.append(SingleObjectId)
                    }
                }
            } else {

                // Log details of the failure
                print("Error: \(error!) \(error!.userInfo)")
            }
        }
    }

This works fine for all other string columns for my parse objects except the ObjectId. It throws an exception error everytime. Why is this?

Rugmangathan · Accepted Answer · 2016-01-25 06:58:55Z

3

Use oneObj.objectId instead of what you tried in the above code.

Change the line let ObjectIdFromParse = oneObj["objectId"] as! String to

let ObjectIdFromParse = oneObj.objectId as! String

answered Jan 25, 2016 at 6:58

Rugmangathan

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Comments

William GP · Accepted Answer · 2016-01-25 08:02:49Z

1

From the Parse documentation on PFObjects

objectId, createdAt, and updatedAt are provided as properties on every PFObject, so you don't subscript them using [""], but instead reach them through .objectId, .createdAt, .updatedAt on your object.

You also don't need to force downcast to a String, as objectId is always a String (as you mentioned). But, you do need to unwrap the optional (saying that you know this objectId exists). Therefore the correct line of code should be:

let ObjectIdFromParse = oneObj.objectId!

edited Jan 25, 2016 at 8:02

answered Jan 25, 2016 at 7:56

William GP

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Comments

Dharman · Accepted Answer · 2022-03-31 14:32:47Z

1

If you want to store a representative common of .objectID, you should use the object's "uriRepresentation" (URL) that refers to that .objectID.

From documentation

func managedObjectID(forURIRepresentation: URL) -> NSManagedObjectID?

As an example, you have: swift 4

do
{
  let entity = try self.context.fetch(fetchRequest())
  let entityObj = entity.last as! Any
  let uriID = entityObj.objectID.uriRepresentation().absoluteString
}
catch
{ 
  print("Error...") 
}

Remember to saveContext() before you get the ID, or you will be given a temporary ID.

https://developer.apple.com/documentation/coredata/nsmanagedobjectid/1391691-temporaryid

You can find more: https://developer.apple.com/documentation/coredata/nspersistentstorecoordinator/1468882-managedobjectid

edited Mar 31, 2022 at 14:32

Dharman♦

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answered May 13, 2020 at 20:07

Wander Filho

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