swiftblockoperationoperationqueue

Updating UI when working with OperationQueue

I have an operation queue setup as follows: 

let queue = OperationQueue()
queue.name = "com.company.myQueue"
queue.qualityOfService = .userInitiated
queue.maxConcurrentOperationCount = 64
...
var current = 0
var totalCount = someArray.count
for i in someArray {
... 
   let op = BlockOperation {
   ... // do some database queries
   current += 1
   }

   op.completionBlock = {
     DispatchQueue.main.async {
     let nData: [String: CGFloat] = ["value": CGFloat(current/totalCount)]
     NotificationCenter.default.post(name:Notification.Name(rawValue: "update"), object: nil, userInfo: nData)
   }

   queue.addOperation(op)
}

In my ViewController I listen for the notification and update a UILabel with the percentage. Problem is though I don't get any intermediate values... it jumps from being 0 directly to 100 once all the operations are done.

What am I doing wrong?

Thanks

Solution

  • The problem is CGFloat(current / totalCount). That does the integer math first, and then converts it to a float. You should flip that around to CGFloat(current) / CGFloat(totalCount).