Unable to sort a Swift array

Question

I'm trying to sort my contacts array by severity

    var contacts: [Contact]?   

    if let customer = CoreDataAccess.sharedInstance.getSavedCustomer() {
       //Cast from NSSet to [Contact]        
       self.contacts = customer.contacts.allObjects as? [Contact]
       self.contacts!.sort({$0.severity < $1.severity}) //error
    }

The compiler errors out at the marked line with the following message:

Cannot invoke 'sort' with an argument list of type '((_, _) -> _)'

I'm not sure what I'm doing wrong because this exact same thing worked in another file. If it helps to explain, the above code crashes when running on the WatchKit interface, but not when used in iOS.

EDIT: severity is an NSNumber

Try reproducing the problem in a dummy project. If it's possible, file a bug report at Apple Bug Reporter. — Vatsal
– Vatsal, Commented Aug 2, 2015 at 8:18

vadian · Accepted Answer · 2019-06-26 14:42:27Z

2

Try to cast the first argument explicit to NSNumber and use the compare: method (I tested it in a Playground)

var contacts: [Contact]?
if let customer = CoreDataAccess.sharedInstance.getSavedCustomer() {
    //Cast from NSSet to [Contact]
    self.contacts = customer.contacts.allObjects as? [Contact]
    self.contacts!.sort { ($0.severity as NSNumber).compare($1.severity) == .orderedAscending }
}

It's even more efficient to declare the relationship as native Swift set Set<Contact> and the attribute as Int, this avoids to call allObjects and the type casts. And declare contacts as non-optional empty array.

var contacts = [Contact]()
if let customer = CoreDataAccess.sharedInstance.getSavedCustomer() {
    self.contacts = customer.contacts.sorted { $0.severity < $1.severity }
}

edited Jun 26, 2019 at 14:42

answered Aug 2, 2015 at 18:04

vadian

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1 Comment

Carpetfizz Over a year ago

Thank you! Casting NSNumber to Int worked perfectly!

Yu-Lin Wang · Accepted Answer · 2015-08-03 14:48:17Z

1

I think the problem is the property of Contact "severity" !

The type of "severity" is your custom type, and it's not implement compare operator like "<"

Since severity is NSNumber We can do this

func <(lhs: NSNumber, rhs: NSNumber) -> Bool {
    return lhs.compare(rhs) == NSComparisonResult.OrderedAscending
}
func >(lhs: NSNumber, rhs: NSNumber) -> Bool {
    return lhs.compare(rhs) == NSComparisonResult.OrderedDescending
}
func ==(lhs: NSNumber, rhs: NSNumber) -> Bool {
    return lhs.compare(rhs) == NSComparisonResult.OrderedSame
}

then the code will works fine.

edited Aug 3, 2015 at 14:48

answered Aug 2, 2015 at 10:30

Yu-Lin Wang

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Comments

avismara · Accepted Answer · 2015-08-02 08:00:36Z

0

Try this:

var contacts: [Contact]?   
if let customer = CoreDataAccess.sharedInstance.getSavedCustomer() {
   //Cast from NSSet to [Contact]        
   self.contacts = customer.contacts.allObjects as? [Contact]
   self.contacts!.sort {
       $0.severity < $1.severity
   }
}

answered Aug 2, 2015 at 8:00

avismara

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