loading images from coredata , tableview is not scrolling smooth - ios

Question

I have six custom cells. 3 cells contain imageView and some labels and others just contains labels. In viewDidLoad, I loaded all data from coredata and refreshing the tableview the problem is when table has cells (without imageview cell) it scrolls smoothly but when we add cell(which has imageview) it scrolls smoothly in down scrolling but it structs when I am up scrolling the tableview.I tried to reduce image quality but didn't work. how to solve this
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell
{
let insuranceCell = tableView.dequeueReusableCell(withIdentifier: "insuranceCell") as! InsuranceCell
let pollutionCell = tableView.dequeueReusableCell(withIdentifier: "pollutionCell") as! PollutionCell
let servicingCell = tableView.dequeueReusableCell(withIdentifier: "servicingCell") as! ServicingCell
let challanPaidCell = tableView.dequeueReusableCell(withIdentifier: "challanPaidCell") as! ChallanPaidCell
let insuranceClaimCell = tableView.dequeueReusableCell(withIdentifier: "insuranceClaimCell") as! InsuranceClaimCell
let fuelRefillCell = tableView.dequeueReusableCell(withIdentifier: "fuelRefillCell") as! FuelRefillCell
let cellArr = sections[indexPath.section].cell
//Loading cell based on array details
switch cellArr[0] {
case is InsuranceDetails:
insuranceCell.setup(object: cellArr[indexPath.row])
return insuranceCell
case is Pollution:
pollutionCell.setup(object: cellArr[indexPath.row])
return pollutionCell
case is Servicing:
servicingCell.setup(object: cellArr[indexPath.row])
return servicingCell
case is ChallanPaid:
challanPaidCell.setup(object: cellArr[indexPath.row])
return challanPaidCell
case is InsuranceClaims:
insuranceClaimCell.setup(object: cellArr[indexPath.row])
return insuranceClaimCell
case is FuelRefills:
fuelRefillCell.setup(object: cellArr[indexPath.row])
return fuelRefillCell
default:
return insuranceCell
}
}
class InsuranceCell: UITableViewCell {
func setup(object : NSManagedObject){
guard let arr = object as? InsuranceDetails else {return}
lbAmountPaid.text = arr.amountPaid
lbAgency.text = arr.agency
lbVehiclevalidfrom.text = arr.vehicleValidFrom
lbVehiclevalidupto.text = arr.vehicleValidUpto
let imageData = arr.insurancePhoto ?? Data()
let image = UIImage(data: imageData)
let compimapge = image?.resized(withPercentage: 0.1)
insurancePhoto.image = compimapge
}

Answer 1

As Fabio says, don't unnecessarily dequeue all the cells all of the time.
However, the image creation and scaling is most likely where the stuttering is coming from. The naming of the parameter in your call to UIImage.resized(withPercentage: 0.1) suggests that your source images are truly massive (you are displaying them at 1/1000th of their original size!?). If the parameter name is misleading and 0.1 really means 1/10th, I suggest renaming the parameter (UIImage.resized(withFraction: 0.1) perhaps).
Having said all that, look to move the image scaling off the main thread. Something like this (un-tested):
class InsuranceCell: UITableViewCell {
func setup(object: NSManagedObject, in table: UITableview, at indexPath: IndexPath) {
guard let arr = object as? InsuranceDetails else {return}
lbAmountPaid.text = arr.amountPaid
lbAgency.text = arr.agency
lbVehiclevalidfrom.text = arr.vehicleValidFrom
lbVehiclevalidupto.text = arr.vehicleValidUpto
// Do time consuming stuff in the background
DispatchQueue.global(qos: .userInitiated).async {
let imageData = arr.insurancePhoto ?? Data()
let image = UIImage(data: imageData)
// This will be where all the time is going. 0.1% suggests your source
// image is massively oversized for this usage.
let compimage = image?.resized(withPercentage: 0.1)
// Always back to the main thread/queue for UI updates
DispatchQueue.main.async {
guard let cell = table.cellForRow(at: indexPath) as? InsuranceCell else {
// The cell we wanted to configure is no longer in view
return
}
// Don't be tempted to write straight to `self.insurancePhoto.image`,
// it may already have been reused for a different row
// if the user is scrolling quickly
cell.insurancePhoto.image = compimage
}
}
}
}
It requires the additional parameters in order to check that updating the cell is still appropriate once the scaling has completed.