Sort by date - Swift 3

Question

I have a func getData() which retrieves core data entity, and I want to sort them by date. How can I apply NSPredicate or Predicate to get the data from CoreData sorted by date?

My core data entity: Entity: Expenses Attributes: - amount - category - date

func getData() {
    let context = appDelegate.persistentContainer.viewContext

    do {
        expenses = try context.fetch(Expenses.fetchRequest())
    } catch {
        print("Cannot fetch Expenses")
    }
}

Thank you for the help!

Answer 1

Predicates are for filtering your search results. To sort them you need to use an NSSortDescriptor. Assuming you have an attribute on your Expenses entity called date of type Date:

func getData() {
    let context = appDelegate.persistentContainer.viewContext  

    let fetchRequest = NSFetchRequest<Expenses>(entityName: "Expenses")
    let sort = NSSortDescriptor(key: #keyPath(Expenses.date), ascending: true)
    fetchRequest.sortDescriptors = [sort]
    do {
       expenses = try context.fetch(fetchRequest)
    } catch {
        print("Cannot fetch Expenses")
    }
}

EDIT: I should have mentioned that the sort selector is added in an array so that multiple sort descriptors can be added if needed. e.g. sort first by date, then by number of legs, then by volume, etc.

Answer 2

You need a sort descriptor to get all the objects in a specific order.

let sectionSortDescriptor = NSSortDescriptor(key: "date", ascending: true)
let sortDescriptors = [sectionSortDescriptor]
fetchRequest.sortDescriptors = sortDescriptors