The array of String property in a managed object constantly nil - ios

Question

First, I'm extracting the content from the text fields into a dictionary:
var dict: [String: String] = [:]
for metricPair in metricStackView.arrangedSubviews {
if metricPair.subviews[0] is UITextField {
let unitTextField = metricPair.subviews[0] as! UITextField
let valueTextField = metricPair.subviews[1] as! UITextField
if let textContent = unitTextField.text, let valueTextContent = valueTextField.text {
let trimmedKey = textContent.trimmingCharacters(in: .whitespacesAndNewlines)
let trimmedValue = valueTextContent.trimmingCharacters(in: .whitespacesAndNewlines)
dict.updateValue(trimmedValue, forKey: trimmedKey)
}
}
}
And I'm saving it to Core Data:
let goal = Goal(context: self.context)
goal.date = Date()
for item in dict {
goal.metrics?.append(item.key)
}
goal.progress.insert(progress)
My managed object looks like this:
extension Goal {
#nonobjc public class func createFetchRequest() -> NSFetchRequest<Goal> {
return NSFetchRequest<Goal>(entityName: "Goal")
}
#NSManaged public var date: Date
#NSManaged public var metrics: [String]?
#NSManaged public var progress: Set<Progress>
}
I keep getting nil for the metrics property of [String] type even before the context is saved. When I log item.key in:
for item in dict {
goal.metrics?.append(item.key)
}
the content is showing up properly.

Answer 1

As far as I can tell from the above code, metrics array is not initialized.
Try replacing this line:
goal.metrics?.append(item.key)
With these lines:
if case nil = goal.metrics?.append(item.key) {
goal.metrics = [item.key]
}
or with simply these lines:
if goal.metrics == nil {
goal.metrics = []
}
goal.metrics?.append(item.key)