If/Else based on existence of object in array? - ios

Question

I want to trigger an else statement if there is no object at the indexPath i look for in an array.
The array is
let exerciseSets = unsortedExerciseSets.sorted { ($0.setPosition < $1.setPosition) }
Then i use let cellsSet = exerciseSets[indexPath.row]
There is a chance, when a user is adding a new cell, that it wont already have an exerciseSet at the indexPath to populate it (adding a new set to an existing array of sets) and so I need to run an else statement to set up a blank cell rather than attempting to populate it and crashing my app.
However if i use if let then i get this error:
Initializer for conditional binding must have Optional type, not
'UserExerciseSet'
Here is the whole function for context if needed:
func configure(_ cell: NewExerciseTableViewCell, at indexPath: IndexPath) {
if self.userExercise != nil {
print("RESTORING CELLS FOR THE EXISTING EXERCISE")
let unsortedExerciseSets = self.userExercise?.exercisesets?.allObjects as! [UserExerciseSet]
let exerciseSets = unsortedExerciseSets.sorted { ($0.setPosition < $1.setPosition) }
if let cellsSet = exerciseSets[indexPath.row] { // this causes a creash when user adds new set to existing exercise as it cant populate, needs an else statement to add fresh cell
cell.setNumber.text = String(cellsSet.setPosition)
cell.repsPicker.selectRow(Int(cellsSet.setReps), inComponent: 0, animated: true)
let localeIdentifier = Locale(identifier: UserDefaults.standard.object(forKey: "locale") as! String)
let setWeight = cellsSet.setWeight as! Measurement<UnitMass>
let formatter = MassFormatter()
formatter.numberFormatter.locale = localeIdentifier
formatter.numberFormatter.maximumFractionDigits = 2
if localeIdentifier.usesMetricSystem {
let kgWeight = setWeight.converted(to: .kilograms)
let finalKgWeight = formatter.string(fromValue: kgWeight.value, unit: .kilogram)
let NumericKgResult = finalKgWeight.trimmingCharacters(in: CharacterSet(charactersIn: "0123456789.").inverted)
cell.userExerciseWeight.text = NumericKgResult
} else {
let lbsWeight = setWeight.converted(to: .pounds)
let finalLbWeight = formatter.string(fromValue: lbsWeight.value, unit: .pound)
let NumericLbResult = finalLbWeight.trimmingCharacters(in: CharacterSet(charactersIn: "0123456789.").inverted)
cell.userExerciseWeight.text = NumericLbResult
}
} else {
cell.setNumber.text = String((indexPath.row) + 1)
}

Answer 1

You could do something crazy like this:
if let cellSet = (indexPath.row < exerciseSets.count ? exerciseSets[indexPath.row] : nil) {
//
}
but it would be more straightforward to do:
if indexPath.row < exerciseSets.count {
let cellSet = exerciseSets[indexPath.row]
...
}

Answer 2

OK, so your problem is that you are trying to access a value in an array that may or may not be there.
If you just try to access the value based on indexPath you can crash because indexPath may refer to a value not there. On the other hand, the array does not return an optional so you can't use if let either.
I kind of like the idea of using an optional, so how about introducing a function that could return an optional to you if it was there.
Something like:
func excerciseSet(for indexPath: IndexPath, in collection: [UserExcerciseSet]) -> UserExcerciseSet? {
guard collection.count > indexPath.row else {
return nil
}
return collection[indexPath.row]
}
and then you can say:
if let cellsSet = exerciseSet[for: indexPath, in: excerciseSets] {
//It was there...showtime :)
} else {
cell.setNumber.text = String((indexPath.row) + 1)
}
Hope that helps you.

Answer 3

Just check the index against your array count:
if indexPath.item < exerciseSets.count {
// Cell exists
let cellsSet = exerciseSets[indexPath.row]
} else {
// cell doesn't exists. populate new one
}