Sort array of custom objects on conditions [duplicate]

I've got an array of custom objects where each object has two files date and subject - I need to write some logic that will sort these objects on a condition.

Condition - It should always sort with the date first. If multiple objects are there with the same date then those records should be sorted by its subject.

How do I do that?

I am successfully able to sort them out either using the date or subject but not sure on how to do it with this condition.

Here's the current code:

let result = results.sorted(by: { (customObject1, customObject2) -> Bool in
    if let dueDate1 = customObject1.date as Date?, let dueDate2 = customObject2.date as Date? {
        return dueDate1.compare(dueDate2 ) == .orderedDescending
    } else if let subject1 = customObject1.subject, let subject2 = customObject2.subject {
        return subject1.localizedCaseInsensitiveCompare(subject2) == .orderedAscending
    }
        return false
 })